Dushoff, Jonathan, Lee Worden, Juan Keymer, and Simon Levin. (2002) 2002. “Metapopulations, Community Assembly, and Scale Invariance in Aspect Space.”. Theoretical Population Biology 62 (4): 329-38.

Worden, Lee, and Simon Levin. (2007) 2007. “Evolutionary Escape from the prisoner’s Dilemma.”. Journal of Theoretical Biology 245 (3): 411-22.