@article {7873,
	title = {Maximum-likelihood estimation of phylogeny from DNA sequences when substitution rates differ over sites},
	journal = {Molecular Biology and Evolution},
	volume = {10},
	number = {6},
	year = {1993},
	note = {PDF},
	pages = {1396-1401},
	keywords = {gamma distribution, ML, phylogenetics, rates, substitution rates},
	author = {Yang, Ziheng}
}
