L. Bujňák, A. Marcin, P. Naď, und T. Mihok, „Effect of supplemental humic acid with urea as a non protein dietary nitrogen source on rumen variables in sheep“, ANIM WELFARE ETOL TARTÁSTECHN, Bd. 16, Nr. 1, S. 1–7, Mai 2020, doi: 10.17205/SZIE.AWETH.2020.1.001.