Talk pages aren’t valid sources in general. In this case the author is dead and an established expert having published in the field, so I guess it’s fine, but I

Talk pages aren’t valid sources in general. In this case the author is dead and an established expert having published in the field, so I guess it’s fine, but I wouldn’t bet. https://en.wikipedia.org/wiki/Wikipedia:Verifiability#Self-published_sources_(online_and_paper) https://en.wikipedia.org/wiki/Wikipedia:Verifiability#Self-p...