Resemblance of psychotic symptoms and syndromes in affected sibling pairs from the irish study of high-density schizophrenia families: evidence for possible etiologic heterogeneity. - Kendler,K.S.; Karkowski-Shuman,L.; O'Neill,F.A.; Straub,R.E.; MacLean,C.H.; Walsh,D. (Am J Psychiatry, 1997)