As Jeremy pointed out correctly, the vast majority of essays by Netty van Gasteren were written in conjunction with Edsger W. Dijkstra and myself. Have a look at the EWD site from Austin and at the WF-files at MathMeth. The approximately 30 chapters of our book on Multiprogramming each have an AvG/WF number, but I think I cannot upload these to the MathMeth site. I know of the existence of a small number of AvG's written by Netty herself, but I don't have these. What I can do is ask her husband Dick.
It's a pity that Jeremy hasn't yet made Netty's PhD thesis available on the site. Therefore I send you a copy along with this mail. Good luck, enjoy, and mail me if I can help. Best wishes,