Ettala, Terttu, and Matti Kreula. “Studies on the Nitrogen Compounds of the Faeces of Dairy Cows Fed Urea As the Sole or Partial Source of Nitrogen”. Agricultural and Food Science 51, no. 1 (January 1, 1979): 506–513. Accessed June 11, 2024. https://journal.fi/afs/article/view/72012.