Butterworth C. A., Resolving "Nyffeler's puzzle" - The intriguing taxonomic position of Blossfeldia, Haseltonia, 2006, 12:3-10, doi: 10.2985/1070-0048(2006)12[3:RNPITP]2.0.CO;2
The analysis of chloroplast sequences and rpoC1 gene structure concerns the phylogenetic position of Blossfeldia. The results support the distinctness of this lineage from the other cacti traditionally grouped in Cactoideae.