E. Oele, W. Apon, M. M. Fischer, R. Hoogendoorn, C. S. Mesdag, E. F. J. de Mulder, B. Overzee, A. Sesoren and W. E. Westerhoff (1983) “Surveying the Netherlands: sampling techniques, maps and their application”, Netherlands Journal of Geosciences, pp. 355-372. Available at: https://njgjournal.nl/index.php/njg/article/view/13396 (Accessed: 4April2026).