Any self-respecting Led Zeppelin fan knows a lot about them with all their connections with the blues and Jimmy Page's time with Yardbirds. And there really is need for a PhD thesis on it. Zep's music is influenced by more than just the blues. Try listening to Zep 3. Ok, Since I've been Loving You, but the rest of the album is very ecelectic. Same for Zep 4, Houses of the Holy, Graffiti and Presence, the last track of which is, yes, another blues but sounds like a self-composed piece (quite brilliant too). So, I say listen to Son House thru' to Zeppelin and you'll hear all the influences just run through all blues artists.