E. OELE; W. APON; M. M. FISCHER; R. HOOGENDOORN; C. S. MESDAG; E. F. J. DE MULDER; B. OVERZEE; A. SESOREN; W. E. WESTERHOFF. Surveying the Netherlands: sampling techniques, maps and their application. Netherlands Journal of Geosciences, p. 355-372, 1 Jan. 1983.