Butterworth C. A., Cota-Sánchez J. H., Wallace R. S., Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation, Systematic Botany, 2002, 27(2):257-270, doi: 10.1043/0363-6445-27.2.257
A Cacteae phylogeny based on the plastid rpl16 intron. The analysis identifies the Aztekium and Geohintonia clade and compares the arrangement of molecular groups with stem structure and earlier classifications.