This order is represented by a single family, Caprimulgidae (nightjars and allies).
Han, K.-L., M.B. Robbins, and M.J. Braun (2010), A Multi-gene Estimate of Phylogeny in the Nightjars and Nighthawks (Caprimulgidae), Mol. Phylogenet.
Evol. 55, 443-453. (abstract)
Sigurdsson, S., and J. Cracraft (2014), Deciphering the diversity and history of New World nightjars (Aves: Caprimulgidae) using molecular phylogenetics,
Zool. J. Linn. Soc. 170, 506-545. (abstract)
White, N.D., G.F. Barrowclough, J.G. Groth, and M.J. Braun (2016), A multi-gene estimate of higher-level phylogenetic relationships among nightjars,
Ornito. Neotrop. . (pdf)