Penchovska, J., Ivanova, M., & Kobakova, A. (1993). Catalogue of environmental non-governmental organizations in Bulgaria: = Katalog na nepravitelstvenite organizacii za opazvane na okolnata sreda v Bălgarija. Publ. House Magazine Anteni u.a.
Chicago-Zitierstil (17. Ausg.)Penchovska, Julietta, Mariana Ivanova, und Antoaneta Kobakova. Catalogue of Environmental Non-governmental Organizations in Bulgaria: = Katalog Na Nepravitelstvenite Organizacii Za Opazvane Na Okolnata Sreda V Bălgarija. Sofija: Publ. House Magazine Anteni u.a, 1993.
MLA-Zitierstil (9. Ausg.)Penchovska, Julietta, et al. Catalogue of Environmental Non-governmental Organizations in Bulgaria: = Katalog Na Nepravitelstvenite Organizacii Za Opazvane Na Okolnata Sreda V Bălgarija. Publ. House Magazine Anteni u.a, 1993.