Burker, G. V. and Tihonova, M. B. 1965. [Maize silage enriched with urea for fattening pigs.] Svinovodstvo 5: 28–30.
Hanson, L. E. and Ferrin, E. F. 1955. The value of urea in a low-protein ration for weanling pigs. J. Anim. Sci. 14f 43–48.
Harbors, L. H., Alvares, A. P., Jacobson, A. I. and Visek, W. J. 1963. Effect of barbituric acid and chlortetracycline upon growth, ammonia concentration and urease activity in the gastrointestinal tract of chicks. J. Nutr. 80: 75–79.
Kornegay, E. T., Miller, E. R., Ullrey, D. E., Vincent, B. H. and Hoefer, J. A. 1965. Influence of dietary urea on performance, antibody production and hematology of growing swine. J. Anim. Sci. 24: 951–954.
Rose, W. C., Smith, L. E., Womack, M. and Shane, M. 1949. The utilization of the nitrogen of ammonium salts, urea and certain other compounds in the synthesis of nonessential amino acids in vivo. J. biol. Chem. 181: 307–316.
Snyderman, S. E. 1967. Urea as a source of unessential nitrogen for the human. In Urea as a Protein Supplement (ed. Briggs, M. H.), Pergamon Press, Oxford, England.
Visek, W. J. 1968. Some aspects of ammonia toxicity in animal cells. J. Dairy Sci. 51: 286–295.
Young, R. J., Griffith, M., Desai, I. D. and Scott, M. L. 1965. The response of laying hens fed low protein diets to glutamic acid and diammonium citrate. Poultry Sci. 44: 1428.