Shi, D.-M., Yang, H.-X., Hu, M.-B., Du, W.-B., Wang, B.-H., & Cao, X.-B. (2009).
Preferential selection promotes cooperation in a spatial public goods game. Physica A: Statistical
Mechanics and its Applications, 388(21), 4646-4650. doi:10.1016/j.physa.2009.07.031.