Starting with a list of the players in the three Interzonals plus the lists on the image to the left (Source: Europe Echecs 1987-07 p.24; it mentions the date on which it was created, 16 June 1987), I worked out which players had qualified from zonals. This is largely documented in C14: 1987-1990 Zonal Cycle, although that page is not as complete as I would have liked.
There are some mismatches between the players who qualified and those who finally played. This gives me some direction for further research.
I also added a new page for C14: 1987-1990 Zonal Cycle Qualifiers. The page is only a stub for now, but I should be able to fill it out the next time I return to this subject.