Some of the Procol posters sponsored by Bill Graham:

BG #92 11/9-11/11/67, by Nicholas Kouninos. Fillmore & Winterland - Procol Harum, Pink Floyd and H.P Lovecraft

BG #93 11/16-11/18/67, by Jim Blashfield.
Doors, Procol Harum, Mt.Rushmore

BG # 143, Thurs Oct 31- Sat Nov 2, 1968, by Lee Conklin. Procol Harum, Santana, Saloom Sinclair

BG #167, 4/3-4/6/69, by Greg Irons
  Procol Harum, Buddy Miles Express & Blues Image at Fillmore West;
April 6, 1969 was Easter Sunday, venue of the great Easter Island recording

BG254 by David Singer.
Procol Harum, Poco, Rod Stewart & the Faces.
Fillmore West 10/28-31/1970