New Musical Express, July 1970: 'Heading for No 1'
Rolling Stone, 3 September 1970
The Miami News, 20 July 1970 (an exceptional piece of writing)
John McFerrin, online
Home reviewed in 2006
The Regal Zonophone albums
Peter Bourne's 2017 reappraisal
More reviews of Procol Harum albums