Verbatim text: Heil, K. D. and J. M. Porter. 1994. Sclerocactus (Cactaceae): A revision. Haseltonia 2: 20–46.
Author: Heil, K.D., Porter, J.M.
Year: 1994
Title: Sclerocactus (Cactaceae): A revision
Journal: Haseltonia
Volume: 2
Pages: 20–46