Garrison, R. W. “Review of Oxystigma Selys With the Synonymy of Oxystigma williamsoni Geijskes (Odonata: Heteragrionidae)”. Zootaxa, vol. 3780, no. 2, Mar. 2014, pp. 347–364, doi:10.11646/zootaxa.3780.2.7.