Vassya Bankova, Gergana Boudourova-Krasteva, Jose M. Sforcin, Xavier Frete, Atanas Kujumgiev, Rita Maimoni-Rodella, Simeon Popov,
Phytochemical Evidence for the Plant Origin of Brazilian Propolis from São Paulo State Zeitschrift für Naturforschung C. ,vol. 54, pp. 401- 405 ,(1999) ,
10.1515/ZNC-1999-5-616