D. Easton, J. Peto, and A. Babiker. Statistics in medicine, 10 (7):
1025-35(July 1991)4288<m:linebreak></m:linebreak>LR: 20061115; PUBM: Print; JID: 8215016; 0 (Contraceptives, Oral); CIN: Stat Med. 2004 Jan 15;23(1):93-104. PMID: 14695642; ppublish;<m:linebreak></m:linebreak>Mesures d'associació.