Kanemoto T., Kashiwada, Y., Kanbara, K., Gotoh, K., Yoshimori, M., Goto, T., Sano, K. and Nakashima, H. : Anti-human immunodeficiency virus activity of YK-FH312 (a Betulinic acid derivative), a novel compound blocking viral mutation. Antimicrob. Agents Chemother. 45 : 1225-1230, 2001.