http://geo.web.ru/druza/index.html

http://www.earthandman.org/bg/ National Museum "Earth and man" - Sofia, Bulgaria

http://www.minerant.org/ Mineral Collectors Page

http://www.catalogmineralov.ru/ Catalogue mineral

Agates from Sudetes - Poland and Czech

Anton Ivanov - HIGH QUALITY MINERALS FROM BULGARIA, RUSSIA, KAZAKHSTAN, ETC.