@book {2005,
	title = {Van Anna Varwers Convent tot Zuiderkerk. Gasthuizen \& Godshuizen in Groningen},
	year = {2005},
	pages = {134},
	publisher = {Studio van Stralen},
	organization = {Studio van Stralen},
	address = {Groningen},
	issn = {90-77957-03-0},
	author = {Werff, E.O. van der and Overbeek, Rita and Havinga, Bea}
}
@book {2003,
	title = {Martini. Kerk en toren},
	year = {2003},
	pages = {203},
	publisher = {Noordboek},
	organization = {Noordboek},
	address = {Groningen},
	issn = {90-3301159-X},
	author = {Werff, E.O. van der}
}
@inbook {2001,
	title = {Kerspel in stad en land},
	booktitle = {Hel en hemel. De Middeleeuwen in het Noorden. Catalogus van de tentoonstelling in het Groninger Museum 13 april - 2 september},
	year = {2001},
	pages = {138-151},
	publisher = {Groninger Museum},
	organization = {Groninger Museum},
	address = {Groningen},
	issn = {90-71691-53-5},
	author = {Werff, E.O. van der},
	editor = {Knol, Egge and Hermans, Jos M.M. and Driebergen, M.}
}
