State of Oman Catalogue
From the internet. Author "Paleograph" 2011
I forgot to comment of the Greyphil catalogues. I have a lot of admiration for collectors like Greyfield & Duester who will spend years seriously documenting and cataloguing a field that is scorned by most "serious" philatelist.
The likes of Erler, who has single-handedly published 17 volumes of a Catalogue of German Revenues (Volume XVIII alone is composed of... 18 volumes !); Bernhard Luerssen who has made a fantastic catalogue of Elleore stamps, another one for the Principality of Seborga, and who is currently working on Ile Barbe and Ile Roy...
Wolfgang Baltus with his series (now 7 volumes) on classic phantoms; Jon Aitchison with his Lundy and Smaller Channel Islands catalogues. Fritz Billigs with his 44 volumes of Philatelic Handbooks; Forbin, Bourdi, Abrams, to name but a few.
It is a pity that the Greyphil catalogues are not readily available, because they document an area that is both intriguing and interesting, and the State of Oman stamps are now found in most collections, being typical "packet material".
I got mine directly from the author, and I don't remember seeing it advertised anywhere. Mine id a PDF file that I computer-printed and got hardbound to fit in my philatelic library. I would love to find an original copy.