Rokicka, K. et al. 2013. Chromatographic separation of oleanolic, ursolic and betulinic acid in plant extracts on amiopropyl silica using aqueous mobile phases. Current Issues in Pharmacy and Medical Sciences. 26, 3 (Sep. 2013), 296–298. DOI:https://doi.org/10.12923/j.2084-980X/26.3/a.12.