@article {7555,
	title = {Generation and maintenance of gradients in taxonomic diversity},
	journal = {Science},
	volume = {164},
	year = {1969},
	note = {reprint},
	pages = {947-949},
	keywords = {diversification, fossil record, gradients, paleontology, taxonomy},
	author = {Stehli, Francis G. and Douglas, Robert G. and Newell, Norman D.}
}
@article {7061,
	title = {Permian reef complex, Tunisia},
	journal = {Brigham Young University Geology Studies},
	volume = {23},
	number = {1},
	year = {1976},
	note = {reprint},
	pages = {75-112},
	keywords = {bakevellia, bakevelliidae, ecology, fossil record, geology, mollusca, paleoecology, paleozoic, permian, pterioida, pterioidea, reef, stratigraphy},
	author = {Newell, Norman D. and Rigby, J. Keith and Driggs, Allan and Boyd, Donald W. and Stehli, Francis G.}
}
