B. J.  Watrous, Pearson, E. G., Smith, B. B., Snyder, S. P., Blythe, L. L., Riebold, T. W., and Hedstrom, O. R., 
“Megaesophagus in 15 llamas: a retrospective study (1985-1993).”, 
Journal of veterinary internal medicine / American College of Veterinary Internal Medicine, vol. 9, no. 2, pp. 92-9, 1995.
 B. J.  Watrous, Pearson, E. G., Smith, B. B., Snyder, S. P., Blythe, L. L., Riebold, T. W., and Hedstrom, O. R., 
“Megaesophagus in 15 llamas: a retrospective study (1985-1993).”, 
Journal of veterinary internal medicine / American College of Veterinary Internal Medicine, vol. 9, no. 2, pp. 92-9, 1995.