Didn't remember the Lucinda song, even though I had the "car wheels..." in my player when it was released. But i gave it a look at youtube and it certainly is a modern blues song!
Zeppelin sold gazillion records. They had the money and in most case, if not all, they settled out of court. Some credits were given in later releases, but not that many. And this is an ethical matter, not only for money. The songs musically were quite different for the common ear and only the fact that they were careless to include whole phrases in the songs, gave them away. eg.The Lemon song lifts a whole Robert Johnson catch phrase" Squeeze my lemon...", but is really a completely different song. But dazed and confused? Nobody's fault but mine? As I said, I really don't care about it in an artistic way. I get my kicks, original or not, if it is good. But the new artists should mention the original composers, as a "hats off" (and Zeppelin actually wrote a song for Roy Harper, called Hats off to Roy Harper, so they felt the need and understood the value of such gestures) And really it is a logical issue. If I play (or "compose") a Dylan or Zeppelin song that they have copyrighted as being their own, shouldn't I expect a legal action against me? But this is all a nice conversation. They don't listen to us and they keep at it.