B. J.  Adams, Burnell, A. M., and Powers, T. O., ?A phylogenetic analysis of \emph{Heterorhabditis} ({Nematoda:Rhabditidae}) based on {Internal} {Transcribed} {Spacer} 1 {DNA} sequence data?, Journal of Nematology, vol. 30, pp. 22?39, 1998.

T. O.  Powers, Todd, T. C., Burnell, A. M., Murray, P. C. B., Fleming, C. C., Szalanski, A. L., Adams, B. J., and Harris, T. S., ?The r{DNA} internal transcribed spacer region as a taxonomic marker for nematodes?, Journal of Nematology, vol. 29, pp. 441?450, 1997.