Wolf, J. B. W., Künstner, A., Nam, K., Jakobsson, M., & Ellegren, H. (2009). Nonlinear
dynamics of nonsynonymous (d(N)) and synonymous (d(S)) substitution rates affects inference of selection.
Genome Biology and Evolution, 1, 308-319. doi:10.1093/gbe/evp030.