Mah, Kenneth; Binik, Yitzchak M (7 January 2001). «The nature of human orgasm: a critical review of major trends». Clinical Psychology Review21 (6): 823–856. doi:10.1016/S0272-7358(00)00069-6. PMID11497209. «Women rated clitoral stimulation as at least somewhat more important than vaginal stimulation in achieving orgasm; only about 20% indicated that they did not require additional clitoral stimulation during intercourse.».
Mah, Kenneth; Binik, Yitzchak M (7 January 2001). «The nature of human orgasm: a critical review of major trends». Clinical Psychology Review21 (6): 823–856. doi:10.1016/S0272-7358(00)00069-6. PMID11497209. «Women rated clitoral stimulation as at least somewhat more important than vaginal stimulation in achieving orgasm; only about 20% indicated that they did not require additional clitoral stimulation during intercourse.».