Kulkarni, M. ., and D. P. . Ghanegaonkar. “A Review of Pretreatments in Anaerobic Digestion and Biogas Quality Improvement”. International Journal of Technical Innovation in Modern Engineering & Science, vol. 4, no. 12, Dec. 2018, pp. 716-20, https://ijtimes.com/index.php/ijtimes/article/view/381.