- document
- Gerrits, H.J. (author), Ellen, W. van (author), Rooij, N.M. de (author), Steenwijk, J.M. van (author) report 1995
- document
- Gerrits, H.J. (author), Rooij, N.M. de (author) report 1994
- document
- Gerrits, H.J. (author), Ruygh, E.F.W. (author) report 1991