@article {545,
	title = {Beitr{\"a}ge zur Kenntniss der Pteropoden},
	journal = {Arch. Naturgeschichte},
	volume = {20},
	year = {1854},
	pages = {241},
	chapter = {196},
	author = {F.H. Troschel}
}
@article {541,
	title = {Vorl{\"a}ufige Mitteilung {\"u}ber die Thecosomata und Gymnosomata der Siboga-Expedition},
	journal = {Tijdsch. Nederl. Dierk.},
	volume = {2},
	year = {1903},
	pages = {117},
	chapter = {111},
	author = {J.J. Tesch}
}
@book {549,
	title = {Pseudothecosomata, gymnosomata and heteropoda (gastropoda)},
	year = {1976},
	pages = {484},
	publisher = {Bohn, Scheltema \& Holkeme Utrecht},
	organization = {Bohn, Scheltema \& Holkeme Utrecht},
	address = {Amsterdam},
	isbn = {9031301760},
	author = {S. Van Der Spoel}
}
