Good grief, it was a joke. I made no claims of "exclusivity" or research. The excellent New Yorker article by Alex Ross (posted earlier in this thread) mentions the link. And, yes, it has been posted multiple times on other music forums as well along with several other tunes which use the "stolen" Am descending progression. It was also first uploaded on YouTube on December 2011. I notice it has received thousands of views fairly recently, which is good.

NEWSFLASH: Estate of Giovanni Battista Granata set to sue Spirit, Led Zeppelin, Davy Graham, Eric Clapton, Dolly Parton, and my grandmother for musical plagiarism. https://www.youtube.com/watch?v=zKpbJ5Kjy2I