Siregar, S., A. D. Hidayaturobbi, B. A. Wijaya, S. N. Listiani, T. Adiningrum, I. Irwan, and A. I. Pratomo. “Laboratory Experiments on Enhanced Oil Recovery With Nitrogen Injection”. Journal of Engineering and Technological Sciences, vol. 39, no. 1, July 2007, pp. 20-27, doi:10.5614/itbj.eng.sci.2007.39.1.2.