Aditiawati, P., A. Pujobroto, I. Rudiansyah, and H. Rahmadi. “Effect of Stimulants on Biogenic Methane Formation and Dynamics of Bacterial Population”. Journal of Mathematical and Fundamental Sciences, vol. 45, no. 3, Nov. 2013, pp. 274-85, doi:10.5614/j.math.fund.sci.2013.45.3.6.