- document
- Strating, J. (author), van Douwen, A.A. (author), van 't Hullenaar, J.W. (author), Wagemans, L.A.G. (author) report 1971
- document
- van 't Hullenaar, J.W. (author), Strating, J. (author) report 1969
- document
- van 't Hullenaar, W.J. (author) report 1968