Lucifer's Friend was formed from the German band Asterix is 1970. According to Discogs, Ride in the Sky was recorded/released November 1970 at Tonstudio Maschen & Windrose-Dumont Time Studio.
According to Dave Lewis in Led Zeppelin: The Concert File (a must-have book!) Led Zeppelin's Immigrant Song was initially worked on in May and June of 1970 at Headley Grange and was premiered at the Bath Festival 28 June 1970. Led Zeppelin began opening their shows with Immigrant Song in July 1970, starting with -- pay attention here -- Germany. Led Zeppelin III was released in October 1970
So... which band could claims of plagiarism be thrown at? I think it's pretty clear. Just sayin'.
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