@book {578,
	title = {Das Pflanzenreich. Regni vegetabilis conspectus. IV. II. Potamogetonaceae},
	year = {1907},
	pages = {184},
	publisher = {Verlag von Wilhelm Engelmann},
	organization = {Verlag von Wilhelm Engelmann},
	edition = {Engler, A.},
	address = {Leipzig},
	author = {Ascherson, P. and Graebner, P.}
}
@book {466,
	title = {Pondweeds of Great Britain and Ireland},
	series = {BSBI Handbook},
	volume = {8},
	year = {1995},
	pages = {350},
	publisher = {Botanical Society of the British Isles},
	organization = {Botanical Society of the British Isles},
	address = {London},
	author = {Preston, C.D.}
}
