To explain a bit more:
The delta yeasts were indead selected and propagated by Sander Maassen when he was member of Triple-W (home brewing club) in Nijmegen at the period around 1995. I was also member of Triple-W at that time. (I still am at this moment). We had a lot of recipes published with these delta yeasts. It started with the delta-X yeast that was indead a very good one with high fermentation grade and neutral taste, however a disadvantage was that it produced a lot of foam that came outside the fermenting vessel. At this moment I have all these yeasts still on agar tubes, (delta x,v,t,p,e,w,m) however I believe that other yeasts are at least as good. By the way deltaM is the "wiekse witte gist"
One thing I really want to know is where the deltaX yeast comes from, but Sander never wanted to tell.
HansH