- document
- Visser, N.J. (author) report 1967
- document
- Visser, N.J. (author) report 1960
- document
- Visser, H. (author) report 1959
- document
- Visser, H. (author) report 1954
- document
- Visser, H. (author) report 1952
- document
- Gerritsma, J. (author), Visser, H. (author), Schneiders, C.C.M. (author) report 1951
- document
- Gerritsma, J. (author), Visser, H. (author), Schneiders, C.C.M. (author) report 1951