@book{67369,
	author = {Dickson, T. A.},
	title = {Studies in Crataegus L. (Rosaceae : Maloidea) XII. Degree and pattern o f phenotypic variation in Crataegus sect Crus-galli in Ontario},
	note = {Sobretiro de : Systematic botany 10 (3: 322-37, 1985.}
}