Kurniati, Tuti, et al. “Total Lactic Acid, Protein, Fat, and Carbohydrates in Curd Kefir and Cow Colostrum Kefir”. Jurnal Biodjati, vol. 5, no. 2, Nov. 2020, pp. 271-80, doi:10.15575/biodjati.v5i2.9668.