Reinhard: "I usually trust what I find in the respective album's sleeve notes. When I'm told that this is imprecise I will gladly amend it"

Yeah, and you're not alone. I'd imagine most people will tend to trust such statements made on recordings by professional folk artists. All the more reason why professional folk artists and telly producers etc. disseminating both the music and info. on the music, have a responsibility both to enthusiasts who buy their records and to the people who made those songs in the first place, to ensure their published information on the songs is accurate and up to date.

In view of the need to make amendments from time to time, you could include a clearly visible disclaimer somewhere on the page explaining precisely what you just have, and that information on some of the reproduced sleeve notes might be out of date in some instances? But as I said before, the sleevenotes you include describing these revival singers own responses to the songs and their history, make interesting reading.