[Congressional Record (Bound Edition), Volume 153 (2007), Part 25]
[House]
[Pages 33719-33722]
[From the U.S. Government Publishing Office, www.gpo.gov]




       BLOOD LEVELS OF MERCURY ARE RELATED TO DIAGNOSIS OF AUTISM

  The SPEAKER pro tempore. Under a previous order of the House, the 
gentleman from Indiana (Mr. Burton) is recognized for 5 minutes.
  Mr. BURTON of Indiana. Madam Speaker, it's late at night here in the 
Capitol, and most of my colleagues are in their offices or have gone 
home. But I want to talk about an issue that's very, very important 
that we've been talking about now for the last 8 years.
  I was chairman of the Government Reform Committee for 6 years, and 
during that time, my grandson became autistic; and we checked to find 
out what was the cause, trying to find out, because my daughter and her 
husband were just extremely upset about it, as we were as grandparents. 
And we found that he had received nine shots in one day, seven of which 
had a product called themarasol, a preservative, in it. And the 
themarasol was 50 percent ethylmercury. And so I decided to have 
hearings to try to find out if the ethylmercury in those vaccines had 
anything to do with the autistic problem my grandson had. And we found, 
by having many, many hearings over a 4-year period, we found that 
scientists from all over the world and leading doctors and educators 
here that work with autistic children, that the mercury in the vaccines 
did contribute to the autistic epidemic that we had.
  We used to have one in 10,000 children that were diagnosed as being 
autistic. One in 10,000. Today the Centers for Disease Control will 
tell you it's one out of 150. It's an absolute epidemic in this 
country. And we have been fighting and fighting and fighting to make 
sure that those families who have been damaged and those children who 
have been damaged by autism get some kind of compensation. And that's 
why, and I think in 1986 we passed what was called the Vaccine Injury 
Compensation Fund, and it took some of the money from the 
pharmaceutical companies when they sold their vaccine products to put 
into this fund to take care of people who are damaged by vaccines. And 
one of the reasons we did that was because of the issue of autism, 
although at that time I didn't know much about it.
  In any event, the Vaccine Injury Compensation Fund has about $3 
billion in it, and the people who's children have been adversely 
affected by mercury and have autism have not been able to get anything 
out of that. They have to go through a process and see a special 
master, and he has to judge whether or not the information that he has 
and the information they have lead them to believe that the mercury in 
the vaccines caused autism. And so far the special masters have not 
been able to ascertain, according to them, that the mercury in the 
vaccines does cause autism.
  Well, last week, 2 years ago, let's see, 4 years ago there was a 
report, 2004, that said that there was definitely no connection between 
the mercury and the vaccinations and the children getting autism. Well, 
this past November, just last month, two doctors, Dr. Catherine DeSoto 
and Dr. Robert T. Hitlan, both very renowned doctors across this 
country, they have Ph.D.s in medicine, they wrote an article in the 
Journal of Child Neurology. And you can't discount this. What they're 
saying is fact. I want to read to you the summary of what they said. 
They said: ``The question of what is leading to the apparent increase 
in autism is of great importance. Like the link between aspirin and 
heart attack, even a small effect can have a major health implication. 
If there is any link between autism and mercury, it is absolutely 
crucial that the first reports of the question are not falsely stated 
and that no link occurs.''
  Now, get this: ``We have reanalyzed the data set forth originally 
reported in 2004 and have found that the original P value was in error 
and that a significant relation does exist between the blood levels of 
mercury and diagnosis of an autism spectrum disorder. Moreover, the 
hair sample analysis results offer some support for the idea that 
persons with autism may be less efficient and more variable at 
eliminating mercury from the blood.''
  The fact of the matter is the mercury in the vaccines has autism. 
It's not the only cause of autism. But now we have scientific evidence 
by two leading doctors in the Journal of Child Neurology that says 
without doubt, the mercury in the vaccines does cause autism, is a 
major contributing factor.
  Well, I've written, contacted Congressman Kucinich, who's chairman of 
the subcommittee that deals with this in the Capitol, and I've also 
contacted the special masters that decide these cases and have urged 
them to re-evaluate all of these cases where people who have autistic 
children have found that the mercury in the vaccines may have been a 
major cause.
  Now we know that it is a cause of autism, and those people who have 
suffered, and those kids who have suffered need to be compensated out 
of the Vaccine Injury Compensation Fund.
  So I'd like to say to my colleagues, I hope you will join me in 
making sure that the information I just read gets out to everybody. 
These kids are going to live to be 50, 60, 70 years old, and unless 
there's some help for them, they're

[[Page 33720]]

going to be a real burden on the taxpayers and on society. We have an 
obligation to make sure they're taken care of.
  I hope all of my colleagues will read this statement tonight and help 
us to change the attitude of our health agencies and the special 
masters dealing with this problem.
  In November 2007, the well-respected scientific journal, the Journal 
of Child Neurology, published an article authored by Drs. M. Catherine 
DeSoto and Robert T. Hiltlan (PhDs), detailing their findings on the 
relationship between mercury and autism spectrum disorders. The article 
was entitled ``Blood Levels of Mercury are Related to Diagnosis of 
Autism: A Reanalysis of an Important Data Set.''
  To summarize the article, Drs. DeSoto and Hiltlan reanalyzed a data 
set the subject of a 2004 study that found no relationship between 
mercury and autism. By reexamining the data set, Drs. DeSoto and 
Hiltlan determined that the conclusions of the 2004 study were wrong, 
and that a relation does exist between the blood levels of mercury and 
diagnosis of an autism spectrum disorder.
  As Drs. DeSoto and Hiltlan noted in their article, there has been a 
marked increase in the diagnosis of autism in this country over the 
last 20 years. In fact we have gone from an autism rate of 1 in 10,000 
to 1 in 150. So, answering the question of what is (and is not) a 
possible contributing cause of autism is crucial, not only to the 
millions of American families currently affected by autism but to 
future generations.
  We simply cannot dismiss or downplay scientific research, which has 
the potential to unlock the mysteries surrounding what is causing our 
Nation's autism crisis. We owe it to the thousands of families living 
with autism to follow the science wherever it may lead.
  That's why in late November, I wrote to the Chairman of the House 
Subcommittee on Domestic Policy, Representative Dennis Kucinich; and 
the Special Masters assigned to the Congressionally-created Office of 
Vaccine Program within the U.S. Court of Federal Claims, alerting them 
to the findings in Drs. DeSoto and Hiltlan's latest research.
  Specifically, I asked the Special Masters to take Drs. DeSoto and 
Hiltlan's latest findings into consideration as they carry out their 
mandate of managing and adjudicating childhood vaccine claims. I asked 
Chairman Kucinich to hold a hearing on the environmental risks of 
mercury in childhood vaccines before the 110th Congress ends.
  Given the high stakes involved, scientific reports discussing a 
connection between blood mercury levels and autism deserve serious 
consideration and review by the medical and scientific community.
  During my tenure as Chairman of the House Committee on Government and 
Reform, I spent 6 years researching and hearing testimony from the 
autism advocacy and scientific communities about the autism epidemic 
sweeping our country. Over and over again, questions of causation, 
namely the use of thimerosal--the mercury-based vaccine preservative--
in childhood vaccines were raised.
  Here's what I learned:
  A number of credible national and international scientists testified 
before the Committee that mercury in vaccines is a contributing factor 
in developing neurological disorders, including, but not limited to, 
modest declines in intelligent quotient, autism, and Alzheimer's 
disease. And the body of evidence to support that conclusion gets 
larger everyday.
  Experience tells us that, as with any other epidemic, while there may 
be underlying genetic susceptibilities, there usually is also some type 
of environmental trigger as well--be it exposure to a virus, fungus, 
heavy metal, or pollutant. There has never, to the best of my 
knowledge, been a purely genetic epidemic.
  Genetics alone cannot explain how we went from 1 in 10,000 children 
with autism spectrum disorders 20 years ago to 1 in 150 today. The 
increase happened far too quickly for a genetic shift.
  As mercury is a known bio-accumulative neurotoxin, it is biologically 
plausible that it is a contributing factor to our Nation's autism 
epidemic.
  Autism has no cure, and while it is a life-changing condition, it is 
not a life-threatening disease. This means that the autistic children 
of today will be the autistic adults and autistic seniors, 20, 30, 50, 
even 70 years from now. Our Nation is ill prepared to deal with the 
complex educational, financial, housing, and health care challenges 
posed by a generation of autistic individuals.
  My only grandson is autistic, so this is an issue that is very close 
to my heart; and for the last several years I have fought hard to raise 
awareness of this disease, and increase research into the causes of 
autism, as well as new treatments for those suffering with autism.
  As a Nation, I believe, we have a collective responsibility to do 
everything we can to not only stop the further spread of this disease 
but to help the millions of children, adults and families afflicted 
with it.

                       Journal of Child Neurology


     Blood Levels of Mercury Are Related to Diagnosis of Autism: A 
                  Reanalysis of an Important Data Set

        (By M. Catherine DeSoto, PhD, and Robert T. Hitlan, PhD)

       The question of what is leading to the apparent increase in 
     autism is of great importance. Like the link between aspirin 
     and heart attack, even a small effect can have major health 
     implications. If there is any link between autism and 
     mercury, it is absolutely crucial that the first reports of 
     the question are not falsely stating that no link occurs. We 
     have reanalyzed the data set originally reported by Ip et al. 
     in 2004 and have found that the original p value was in error 
     and that a significant relation dose exist between the blood 
     levels of mercury and diagnosis of an autism spectrum 
     disorder. Moreover, the hair sample analysis results offer 
     some support for the idea that persons with autism may be 
     less efficient and more variable at eliminating mercury from 
     the blood.
       Keywords: autism; mercury; environmental health; 
     neurotoxin; neurodevelopment; blood.
       There is a marked increase in the diagnosis of autism. The 
     question of what is (and is not) related to this increase is 
     crucial to millions of persons affected by the disorder. This 
     article reanalyzes an original data set regarding the 
     relation between blood levels of mercury and diagnosis of an 
     autism spectrum disorder (ASD) by Ip et al. based on our 
     finding of discrepancies in the original article.\1\
       A review of what is known about the neurotoxic effects of 
     mercury is beyond the scope of this paper,\2\ but the 
     observable symptoms of acute mercury poisoning have been 
     reported to match up with many of the problems observed in 
     autism.\4\ Furthermore, mercury poisoning has sometimes been 
     presumptively diagnosed as autism of unknown etiology until 
     the mercury poisoning has been uncovered.\4\ Because there 
     has been a several-fold increase in environmental mercury 
     exposure, the hypothesis that the rise in autism could be 
     related to an environmental increase in mercury levels is a 
     reasonable one to pursue. Autism may result from a 
     combination of genetic susceptibility (perhaps in the form of 
     reduced ability to remove mercury or other neurotoxins from 
     the system) and environmental exposure at key times in 
     development.5,7 This would mean a generalized 
     increase in mercury levels would be expected to co-occur with 
     a generalized increase in autism. but some people exposed to 
     relatively high mercury would not be affected if, for 
     example, their bodies were very efficient eliminators of such 
     toxins. Only if an exposed infant or fetus also had a genetic 
     susceptibility that makes one less able to remove mercury (or 
     other heavy metals) would normal levels of mercury exposure 
     lead to problems. Alternatively, it could be that genes that 
     help detoxify get switched on and start to express themselves 
     a little later than normal in those genetically predisposed 
     to autism; or perhaps. autism results from some combination 
     of these theories.
       Nevertheless, if mercury does play any causal role in 
     facilitating a diagnosis of autism, there would likely be at 
     least some relation between high mercury measured in the 
     blood and symptoms of autism even if ability to metabolize 
     mediates the relationship between exposure and neural 
     toxicity. This is because even if exposure is identical, 
     those who remove mercury less effectively should still have 
     higher levels in the blood. Interestingly, results of hair 
     samples could be expected to be somewhat mixed. The level of 
     mercury in hair may be better understood as an indication of 
     how much mercury has been removed by the body as opposed to 
     the level in the body.\6\ If people are approximately equal 
     in their ability to remove circulating mercury from the 
     bloodstream, then these 2 indicators should match up closely, 
     but if a person's ability to excrete is low, their hair 
     samples might not be elevated even when their blood levels 
     are high.
       Fido and Al-Saad found that mercury levels in hair samples 
     were higher in children diagnosed with autism.\8\ These 
     children were aged 4 to 7. In contrast, Kern et al. reported 
     that mercury hair levels were not significantly different, 
     but were lower at a marginally significant level.\9\ Kern et 
     al. used younger children, ages 1 to 6. Holmes et al. 
     performed the most direct test of the hypothesis that 
     autistic children may be deficient in terms of ability to 
     remove mercury from circulation.\6\ This study estimated 
     mercury exposure of the mothers via a mercury exposure survey 
     questionnaire. They then analyzed the first haircuts of the 
     autistic children and a group of controls (the first haircuts 
     would reflect mercury excretion in utero and very early 
     life). In the autistic group, severity of autism was 
     inversely related to hair mercury levels. This means that the 
     more severe autistic cases actually had less excretion of 
     mercury. Furthermore,

[[Page 33721]]

     among the normal children, hair levels of mercury were 
     correlated to the mother's mercury exposure (as would of 
     course be expected). But among the autistic children, there 
     was no linear relation between the mother's mercury exposure 
     and excretion of mercury in the hair. As the authors state, 
     this pattern of results is easily understood if one considers 
     ``detoxification capacity of a subset of infants,''\6\ such 
     that the bodies of those diagnosed with autism appeared to be 
     less able to excrete and/or metabolize the mercury they were 
     exposed to.
       As the rise in autism is relatively recent, it is not 
     surprising that research into the etiology has not kept pace. 
     Indeed, there are few published articles that consider blood 
     levels of children with mercury that utilize a control group; 
     a psycInfo search using the words ``autism,'' ``mercury,'' 
     and ``blood'' yields only one hit.\1\ Given the high stakes 
     involved, it is crucial that early reports of the connection 
     between blood mercury levels and autism not be misstated. 
     Even a small effect size would be of great theoretical and 
     practical consequence.
       In 2004, Ip et al. reported that no relationship existed 
     between mercury blood levels and diagnosis of autistic 
     spectrum disorder among a group of children with an average 
     age of approximately 7 years. While attempting to estimate 
     the effect size based on the Ip et al. statistics, we 
     realized that the numbers reported by Ip et at could not be 
     correct. The means and standard deviations reported in the 
     2004 article yielded an easily significant t value (autism 
     mean = 19.53 nmol/L, SD = 5.6, n = 82; control mean = 17.68 
     nmol/L, SD = 2.48, n = 55 gives a t = 2.283, two-tailed P = 
     .024 or one-tailed P = .012). Ip et al. wrote that the P 
     value was ``(P) = .15,'' 1(p432) and that their 
     data indicate ``there is no causal relationship between 
     mercury and as an environmental neurotoxin and autism.''\1\ 
     After the error was brought to the attention of the authors, 
     a new analysis was conducted by the original authors and they 
     found the original t test to be in error and the P value to 
     be a mistake (refer to Erratum, p. 1324). Based on their 
     corrected analysis, the authors report the revised P value 
     for their t test to actually be P = .056. We disagree on 
     several grounds that these data indicate no significant 
     effect exists, and report on a completely new reanalysis of 
     the original data set.


                                Methods

       Outliers were removed prior to statistical analysis. An 
     outlier is defined as a score that is ``substantially greater 
     or less than the values obtained from any other 
     individual.''\10\ Outliers have an unduly large influence on 
     the outcome of a statistical test. What actually qualifies as 
     an outlier differs depending on the research question and the 
     statistician analyzing the results; however, values greater 
     than 3 standard deviations either above or below the mean 
     generally qualify as extreme cases.\11\ Within the Ip et al. 
     data, there were 2 such values that were not removed prior to 
     our reanalysis. These 2 values were more than 3 standard 
     deviations above the mean, and both of these values were far 
     from any other score. (Other scores were within 3 points of 
     the next individual; these 2 scores were each 15 or more 
     points away from any other score in the distribution.) To 
     avoid the appearance that these 2 outliers were removed to 
     influence the statistical outcome as opposed to objective 
     criteria for cleaning a data set, it should be noted that the 
     biggest outlier of the 2 was an unusually high blood mercury 
     level of 98, which was in the autistic group. To be clear--if 
     anything, removal of the outliers resulted in a more 
     conservative test as it actually decreased the mean 
     difference between the 2 groups.


                                Results

       Logistic regression was performed using blood mercury level 
     as the predictor and the autistic/control group as the 
     criterion. Results of this reanalysis indicate that blood 
     mercury level can be used to predict autism diagnosis. Data 
     included: r = .20, r\2\ = .04, F(1, 133) = 5.76, P = .017. 
     This finding indicates that there is a statistically 
     significant relationship between mercury levels in the blood 
     and diagnosis of an autism spectrum disorder.
       There was no difference in the mean hair levels where 
     t(l35) = .24 and one-tailed P = .40; this is essentially the 
     same result reported in the original article. However, given 
     that hair levels would normally be expected to be highly 
     correlated to blood levels, it might be surprising that blood 
     levels could predict an autism spectrum diagnosis, but that 
     hair mercury levels could not. Indeed, hair and mercury 
     levels for the full sample were correlated (r = .86, P < 
     .001) indicating that about 75% of the variance in hair 
     levels was accounted for by the mercury level in the blood. 
     To us, the question turned to what the other 25% of the 
     variance might be due, and whether the assumptions of the t 
     test were violated. Although not the central focus of this 
     report, these results could certainly help to inform future 
     researchers of the nature of the relation between autism and 
     mercury, and we include this information for completeness.
       Exploratory Analysis. If one hypothesizes that persons with 
     autism are less able to excrete mercury, especially when 
     their blood levels get in the higher range, one might expect 
     that the correlation between blood and hair levels would 
     break down at the higher blood levels among the autism 
     spectrum group (a type of heteroscedasticity).\5\ Another way 
     of looking at it, the relationship between blood level and 
     hair excretion may be different for persons with autism than 
     those without autism. Levine's test of equality of variance 
     indicated the variance in hair mercury was not evenly 
     distributed between the autism and control groups (F = 5.98, 
     P = .017). We calculated the correlation for persons whose 
     circulating levels of mercury were in the top quartile 
     separately for the autism and control groups. The correlation 
     between blood and hair levels of mercury was r = .91 for the 
     control group (accounting for 84% of the variance). For the 
     autistic group, the correlation was r = .73, meaning only 
     about 55% of the variance in the hair mercury levels was 
     attributable to the blood mercury level differences.
       To check the hypothesis that hair excretion was overall 
     lower than would otherwise be predicted based on a certain 
     blood level in the autistic group, a best fit regression line 
     was calculated (y = 10.3, x = -2.48) indicting that for each 
     unit increase in hair level, blood level increased by 10.3 
     units. Attest on the residuals showed that autistic 
     participants were significantly more likely to have lower 
     hair mercury levels than would be predicted as a function of 
     their blood levels, t(133) = -2.92, P < .005; see Figure 1). 
     It should also be noted that the presence of unequal 
     variances or nonrandom residuals (in this case, autistic 
     persons are both more likely to have greater variability at 
     high levels of circulating mercury and a lower hair value for 
     a given blood level) are both violations of important 
     assumptions of the t test; a t test of hair mercury is 
     therefore probably not a valid means to predict autism 
     diagnosis as a function of mercury exposure. We performed an 
     analysis of covariance (ANCOVA) with autism diagnosis as the 
     independent variable and hair mercury level as the dependent 
     predictor using blood levels as a covariate. Results indicate 
     that hair level may be related to diagnosis of autism, not as 
     a predictor in terms of absolute value, but such that for 
     equivalent circulating levels of mercury in the body, those 
     with ASD excreted less than normal such that F(1,134) = 3.9 
     and P = .05. To sum, the relationship between blood levels of 
     mercury and mercury excreted in the hair is reduced for those 
     with autism compared with nonautistic persons; furthermore, 
     the difference between autistic and nonautistic persons is 
     most pronounced at high levels of mercury.


                               Discussion

       In statistics, obtaining a probability value of P < .05 
     indicates that the obtained test statistic (based on one's 
     sample) is extremely unlikely (less then 5% chance) to have 
     been obtained by chance alone. By convention, this value is 
     usually set at .05 (as a balance of type 1 and type 2 
     errors); however, this value is, in fact, arbitrary and 
     statistical probability tables for hypothesis testing always 
     include a range of probability values--not only probability 
     at the .05 level. Given that this is the first direct test of 
     this hypothesis and considering the potential importance of 
     finding a relation between mercury blood levels and autism, 
     it is just as important to avoid a false negative as a false 
     positive. As the original authors have now currently 
     calculated, the obtained difference suggests that there is 
     probably a real difference (specifically that the chance that 
     a real effect exists is about 94%, or, conversely, that the 
     chance null effect is true is less than 6%, which misses the 
     conventional .05--or 5%--mark of statistical significance). 
     Given the close value to conventional significance, most 
     researchers would not call this a firm rejection of the 
     hypothesis, but might say it was marginally significant. Most 
     researchers facing a P value of .056 would not want to 
     categorically state that results ``indicate that there is no 
     casual relation between mercury level . . . and autism.''\1\ 
     It concerns us that the original authors would want to let 
     this conclusion stand in light of the new P value (which 
     differs markedly from the .15 previously reported in 2004).
       Another issue to consider is the question of a one-tailed 
     or a two-tailed hypothesis test. Usually, researchers use a 
     two-tailed test, which tests if there is a ``difference'' 
     between 2 groups. However, when the literature leads a 
     researcher to propose a specific direction of the difference, 
     a one-tailed test is called for, ``Often a researcher begins 
     an experiment with a specific prediction about the treatment 
     effect. For example, a special training program is expected 
     to increase student performance, or alcohol consumption is 
     expected to slow reaction times . . . The result is a 
     directional test, or what is commonly called a one-tailed 
     test.''\10\
       Whether to use a one-tailed test or a two-tailed test can 
     be decided based on considering what would happen if the 
     results ended up in the opposite direction of what one 
     suspects. In this case, it would mean that the blood mercury 
     levels were lower in the autistic group. Would this support 
     the original hypothesis? (No!) However, if this were to 
     happen, that is, if the autistic group were significantly 
     lower in their blood mercury levels than the normal group, 
     the researchers would find themselves in the incongruous

[[Page 33722]]

     position of having to accept their hypothesis that autism is 
     related to elevated levels of mercury in the blood! The key 
     point here is that their hypothesis was directional, and a 
     one-tailed test should have been used. In this case, the just 
     missed significance of their new analysis using a two-tailed 
     t-test (P = .056) would have reached a conventional level of 
     statistical significance (with P <.03).
       Although the statistics can be tedious, the bottom line is 
     that only by an apparent error in the original data analysis 
     was the original lack of effect found. The authors' revised 
     calculation (t test) still has problems (two-tailed test for 
     a directional hypothesis, not removing clear outliers). And 
     finally, the willingness to characterize a t test with a .056 
     level of statistical significance as no effect is 
     questionable, especially in this particular case.
       Of utmost importance (which outweighs the discomfort of 
     writing about an error made by colleagues whom we know are 
     generally competent researchers) is that potential 
     researchers who are trying to understand what is and is not 
     behind the rise in autism are not misled by even the 
     slightest misinformation. It is imperative that researchers, 
     medical professionals, and the public at large have the full 
     set of information. To put it in perspective, the connection 
     between taking aspirin and prevention of heart attack has an 
     effect size equal to .038 which represents an effect size 
     approximately equal to what we find between circulating 
     levels and ASD diagnosis in this age group.\12\ Just as 
     important is the fact that for those physicians in the 
     aspirin group who did have a heart attack, the heart attack 
     was less likely to be fatal. The effect size for this latter 
     effect was .08 and did not represent a significant difference 
     from the placebo group by traditional dichotomous 
     significance testing.\13\ Yet, this does not mean no effect 
     exists or that the effect is not of practical importance. We 
     would encourage all researchers to not only report whether a 
     test of mercury and autism reaches significance with the 
     sample size used, but to report the exact statistic and also 
     effect sizes to help future researchers resolve all the 
     factors involved in the etiology of autism.


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       7. Walker SJ, Segal J, Aschner M. Cultured lymphocytes from 
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       8. Fido A, Al-Saad S. Toxic race elements in the hair of 
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       9. Kern JK, Grannerman BD, Triverdi MH, Adams J. 
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       10. Gravetter FJ, Wallnau LB. Essentials of Statistics for 
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       11. Tabachnik B, Fidell LS. Using Multivariate Statistics. 
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