Gao, Yuan; Xu, Hongyu; Lu, Zhenming; Xu, Zhenghong (November 2009). «Quantitative determination of steroids in the fruiting bodies and submerged-cultured mycelia of Inonotus obliquus». Se Pu27 (6): 745–749. ISSN1000-8713. PMID20352924.
Gao, Yuan; Xu, Hongyu; Lu, Zhenming; Xu, Zhenghong (November 2009). «Quantitative determination of steroids in the fruiting bodies and submerged-cultured mycelia of Inonotus obliquus». Se Pu27 (6): 745–749. ISSN1000-8713. PMID20352924.
Alakurtti, Sami; Mäkelä, Taru; Koskimies, Salme; Yli-Kauhaluoma, Jari (September 2006). «Pharmacological properties of the ubiquitous natural product betulin». European Journal of Pharmaceutical Sciences29 (1): 1–13. doi:10.1016/j.ejps.2006.04.006. ISSN0928-0987. PMID16716572.