@article {7347,
	title = {Les Ambrosia adventices en Europe occidentale},
	journal = {Bull. Jard. Bot. {\'E}tat Bruxelles},
	volume = {18},
	year = {1947},
	month = {1947///},
	pages = {305 - 315},
	author = {A. Lawalr{\'e}e}
}
@article {7229,
	title = {Revision of the North American species of Erigeron, north of Mexico},
	journal = {Brittonia},
	volume = {6},
	year = {1947},
	month = {1947///},
	pages = {121 - 300},
	author = {A. Cronquist}
}
