Gwynne cites Ander 1939, Zeuner 1939, Judd 1947, Key 1970, Ragge 1977 and Rentz 1991 as supporting the two-part scheme (Ensifera, Caelifera) in his 1995 paper.[9]
Gwynne, Darryl T. Phylogeny of the Ensifera (Orthoptera): a hypothesis supporting multiple origins of acoustical signalling, complex spermatophores and maternal care in crickets, katydids, and weta. Journal of Orthoptera Research. 1995, 4 (4): 203–218. JSTOR 3503478.
Prokop, Jakub; Nel, André; Hoch, Ivan. Discovery of the oldest known Pterygota in the Lower Carboniferous of the Upper Silesian Basin in the Czech Republic (Insecta: Archaeorthoptera). Geobios. 2005, 38 (3): 383–387. doi:10.1016/j.geobios.2003.11.006.