Do you know off any reliable databases that store doujinshi metadata (like titles, authors, release date, etc.)? With more and more copyright purges, nh and ex are getting unreliable for research purposes (and this time I mean real research purposes, as in knowing what a certain author has done), but a site only storing the data, not the stuff itself is surely not a copyright concern.
Back in the day before nh I've used doujinshi.org, but that was not very well maintained last couple years, then closed down recently.