Hasdar, M., and Y. D. Rahmawati. “The Variance of Strong Acid and Long Time Soaking Solutions on Quality of PH and Protein Gelatin of Sheep Skin”. Agrisaintifika: Jurnal Ilmu-Ilmu Pertanian, vol. 1, no. 2, Dec. 2017, pp. 88-96, doi:10.32585/ags.v1i2.44.