Hartl W. P., Klapper H., Barbier B., Ensikat H. J., Dronskowski R., Müller P., Ostendorp G., Tye A., Bauer R., Barthlott W., Diversity of calcium oxalate crystals in Cactaceae, Canadian Journal of Botany, 2007, 85(5):501-517, doi: 10.1139/B07-046
A comparative study of the mineral forms and shapes of calcium oxalate crystals in 251 cactus species and subspecies. The authors used X-ray diffraction and light, polarising and scanning microscopy. For Brachycereus nesioticus, they documented calcium oxalate dihydrate crystals, including bipyramids and druses. The author's full text shared on ResearchGate was the basis for the reading.