Swanepoel, W.; Manzitto-Tripp, E. A. .; Dexter, K. G.; van Wyk, A. E. Petalidium Etendekaense (Acanthaceae), a New Species from Namibia, With Notes on the Taxonomic Identity of P. glutinosum. Phytotaxa 2024, 636, 35-47.