Vos, P.C. 1999, The Subatlantic evolution of the coastal area around the Wijnaldum-Tjitsma terp. With a contribution by B.A.M. Baardman. In: J.C. Besteman, J.M. Bos, D.A. Gerrets, H.A. Heidinga & J. de Koning (eds), The excavations at Wijnaldum. Reports on Frisia in Roman and Medieval times.Volume I, Rotterdam/Brookfield, 33-72.