Wikipedia has this to say about Machine Head.
http://en.wikipedia.org/wiki/Machine_Head_%%28album%%29#_note-0
"It is commonly cited as one leg of the 'Holy Trinity' of hard rock,
the other two being Led Zeppelin's (Led Zeppelin IV) and Black
Sabbath's Paranoid.[1]"

The cite is for this article at mp3.com:
http://www.mp3.com/albums/4396/summary.html

One article does not equal "commonly cited".

Where's Dark Side of the Moon?

Is there any sort of consensus on usenet regarding this claim?

Swill