See below for some info; although it's about microfilm it's relevant. Note the date.(posted 8695 days ago)http://palimpsest.stanford.edu/byorg/abbey/an/an12/an12-5/an12-507.html
A month or two ago Doug Nishimura posted some new findings and recommendations on rec.photo.darkroom, both as just posts and some as Q&A with Richard Knoppow. A deja.news search would probably turn those up.
Wilhelm is apparently ignoring everything but printer papers, inks etc, most likely because that's where the money is.