Hi jag,
I'm back from a little hol.

You only have to look at a site like the Bodleian to see that they often altered the titles and rewrote the verses, mixing and matching wherever there was a penny to be gained. Recycling is by no means a new idea. The main culprits were the broadside writers but even the top notchers weren't held back from pinching material from wherever, just as they have always done. What we could add to the database soon is where the plots have been recycled from earlier sources such as with The Tidy Cow, or Keach i' the Creel or 'Bramble Briar'.

As for earlier references in other literature, we do try to flag this up when we come across it. Still a lot to do and we (assistance from Steve Roud and Martin Graebe) are always grateful for any corrections or suggestions or even help from anyone with access to collections not currently available online such as Harvard.