Lopes, L. E., and L. P. Gonzaga. “Morphological Data Support the Recognition of Four Species in the Genus Sirystes Cabanis &Amp; Heine, 1859 (Aves: Tyrannidae)”. Zootaxa, vol. 4127, no. 3, June 2016, pp. 401–431, doi:10.11646/zootaxa.4127.3.1.