Sharma, R. S., and P. C. Shukla. “Effect of Dietary Protein and Non Protein Nitrogen on Rumen Proteolytic and Ureolytic Activities”. The Indian Journal of Nutrition and Dietetics, vol. 10, no. 6, Nov. 1973, pp. 299-02, https://informaticsjournals.com/index.php/ijnd/article/view/10758.