The work I did up to 1992 has been published in several articles but can also be found in my PhD thesis. In my thesis the results are pushed to the limit, they are put in the most general framework.
Defense: Leiden University, June 24, 1992.
A revision appeared as CWI Tract 113, CWI, Amsterdam, 1995. (review from MR; review from JORS; order information)