GOOT, A. van der. Ph.H. Breuker, M. Zeeman, Freonen om ds. J. J. Kalma hinne. Stúdzjes, meast oer Fryslân, foar syn füfensantichste jierdei. BMGN - Low Countries Historical Review, [S. l.], v. 100, n. 1, p. 79–81, 1985. DOI: 10.18352/bmgn-lchr.2542. Disponível em: https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-102760. Acesso em: 24 apr. 2024.