Kirwan, G.M., Schweizer, M. and Copete, J.L. 2015.

Multiple lines of evidence confirm that Hume’s Owl Strix butleri (A. O. Hume, 1878) is two species, with description of an unnamed species (Aves: Non-Passeriformes: Strigidae)

. Zootaxa. 3904, 1 (Jan. 2015), 28–50. DOI:https://doi.org/10.11646/zootaxa.3904.1.2.