On methodological issues regarding 47,+21 paternal age data.
D000293:Adolescent; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010331:Paternal Age; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012307:Risk Factors; D013223:Statistics as Topic