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Pellock JM, Morton LD.Pellock JM, et al. Among authors: morton ld.Ment Retard Dev Disabil Res Rev. 2000;6(4):309-23. doi: 10.1002/1098-2779(2000)6:4<309::AID-MRDD10>3.0.CO;2-I.Ment Retard Dev Disabil Res Rev. 2000.PMID: 11107196Review.