Template:Butterworth, Cota-Sanchez & Wallace, 2002
- Butterworth, C.A., Cota-Sanchez, J.H. & Wallace, R.S. 2002. Molecular systematics of tribe Cacteae (Cactaceae: Cactoideae): a phylogeny based on rpl16 intron sequence variation. Systematic Botany 27(2): 257–270. JSTOR PDF.