D. H. M.  Cumming and Cumming, G. S., ?Ungulate community structure and ecological processes: body size, hoof area and trampling in African savannas?, Oecologia, vol. 134, pp. 560-568, 2003.

K. D.  Floate, Wardhaugh, K. G., Boxall, A. B. A., and Sherratt, T. N., ?Fecal residues of Veterinary Parasiticides: nontarget effects in the Pasture environment?, Annual Review of Entomology, vol. 50, pp. 153-179, 2005.

A.  Vlassoff, Leathwick, D. M., and Heath, A. C. G., ?The epidemiology of nematode infections of sheep?, New Zealand Veterinary Journal, vol. 49, pp. 213-221, 2001.