There's an impressive amount of work behind this songbook, so thank you very much for that.

BUT for every song there is just one set of lyrics as if it were the authoritative version of the song, and no source or history is given for it, as if it fell on us from heaven. In three of the four examples I checked, the lyrics don't match what's sung in the video shown, so my first guess that the video was the implied source for the lyrics was wrong.