Mayr, Gerald (2005): "Old World phorusrhacids" (Aves, Phorusrhacidae): a new look at Strigogyps ("Aenigmavis") sapea (Peters 1987). PaleoBios (Berkeley)25(1): 11-16 HTML abstract
Alvarenga, Herculano M. F. & Höfling, Elizabeth (2003): Systematic revision of the Phorusrhacidae (Aves: Ralliformes). Papéis Avulsos de Zoologia43(4): 55-91 PDF fulltext
Mayr, Gerald (2007). Synonymy and actual affinities of the putative Middle Eocene "New World vulture" Eocathartes Lambrecht, 1935 and "hornbill" Geiseloceros Lambrecht, 1935 (Aves, Ameghinornithidae). Paläontologische Zeitschrift 81, 457-462.[1]