A chronic, low-dose regimen of the antiprogestin ZK 137 316 prevents pregnancy in rhesus monkeys. - Zelinski-Wooten MB; Chwalisz K; Iliff SA; Niemeyer CL; Eaton GG; Loriaux DL; Slayden OD; Brenner RM; Stouffer RL (Human reproduction (Oxford, England), 1998)