P. J.  Waniek, Hendgen-Cotta, U. B., Stock, P., Mayer, C., Kollien, A. H., and Schaub, G. A., ?Serine proteinases of the human body louse (Pediculus humanus): sequence characterization and expression patterns?, Parasitology research, vol. 97, no. 6, pp. 486 - 500, 2005.