Syafila, M., M. Handajani, and A. Prayascitra. “The Effect of Nitrogen Gas Flushing on Intermediate Products Formation in Acidogenic Stage of Anaerobic Process of Cocoa Sweatings”. Journal of Engineering and Technological Sciences, vol. 42, no. 2, Sept. 2013, pp. 129-36, doi:10.5614/itbj.eng.sci.2010.42.2.2.