Pyrrole-type compounds from the flowers of Calotropis gigantea - Tran, Hoai Tu; Dang, Phu; Le, Huu Tho; Do Van, Nhat Truong; Nguyen, Xuan Hai; Nguyen, Thanh Mai; Nguyen, Trung Nhan (VNUHCM Journal of Advanced Research in Natural Sciences, 2023)