Many covers have been scannered from my own collection.
Many other covers have been taken from the net, in particular from these sites:
Info/timing/cat.#s are taken from my personal collection and, in particular, from the Pet Shop Boys Discography (which I have several times collaborated to) originally compiled by Christian Bartholdsson and long updated by Ernie Longmire (Lazlo Nibble) and then conducted by Steffen Gartner 'TheGardner'.
Please ask permission before using pics taken from this site.
You can find here the almost-official updated pricing guide.