@article {3069,
	title = {Symbiosis in fern prothallia},
	journal = {Amer. Naturalist},
	volume = {42},
	year = {1908},
	month = {1908///},
	pages = {154 - 165},
	author = {Campbell, D. H.}
}
@article {3073,
	title = {Studies on the Ophioglossaceae},
	journal = {Ann. Jard. Bot. Buitenzorg},
	volume = {21},
	year = {1907},
	month = {1907///},
	pages = {138 - 194},
	author = {Campbell, D. H.}
}
