This list will hopefully includes a lot of important URTEXT edition of tunebooks that were in print within the past years but are now out of print.
One may find them in large libraries.
Alternatively one may inquire the Internet, which can access inventories of distributors and second-hand book stores.
... one may find them here!
Individual tunes can be separately found in this site in ABC format together with annotation, comments, anecdotes and semantic links to alternative titles, alleged composers and/or geographical provenance, of the same tune.
Tunebooks listed here are freely downloadable and ready for printing in Portable Document Format.
Lilypond and LaTeX were the tools used to typesetting music.
More to come...