Soltan, M.A., et al. “Effect of Dietary Rumen Protected Methionine and Or Choline Supplementation on Rumen Fermentation Characteristics and Productive Performance of Early Lactating Cows”. Pakistan Journal of Nutrition, vol. 11, no. 3, Feb. 2012, pp. 221–230, https://doi.org/10.3923/pjn.2012.221.230.