Gymnocalycium ferox Gymnocalycium hybopleurum var. ferox Gymnocalycium mostii subsp. ferocior Gymnocalycium hybopleurum var. breviflorum Gymnocalycium hybopleurum var. centrispinum Gymnocalycium hybopleurum var. ferocior
World Flora Online, http://www.worldfloraonline.org/, accessed June 20, 2024