- document
- Heeger, H. (author) book 1992
- document
- Van der Zon, F. (author) book 1991
- document
- Heeger, H. (author), Leenhouts, H. (author) book 1991
- document
- Zwartenkot, R. (author) book 1989
- document
- Heeger, H. (author) book 1989
- document
- Heeger, H. (author) book 1988
- document
- Van der Zon, F. (author) book 1986
- document
- Van der Heijden, H.M.H. (author) book 1986