Referencias

cactusgarden.ru
http://cactusgarden.ru/gallery/gymnocalycium.html

troutsnotes.com
http://troutsnotes.com/tag/gymnocalycium/

plantis.info gymnocalycium-mihanovichii
https://plantis.info/es/gymnocalycium-mihanovichii/

plantis.info gymnocalycium-baldianum
https://plantis.info/es/gymnocalycium-baldianum/

cactus-art.biz Gymnocalycium_baldianum
http://www.cactus-art.biz/schede/GYMNOCALYCIUM/Gymnocalycium_baldianum/Gymnocalycium_baldianum/Gymnocalycium_baldianum.htm

cactus-art.biz Gymnocalycium_denudatum
http://www.cactus-art.biz/schede/GYMNOCALYCIUM/Gymnocalycium_denudatum/Gymnocalycium_denudatum/Gymnocalicium_denudatus.htm