Literature
Queen Victoria Issues (GB Overprint Society Study Paper 1) by R. Malim, 1998
Cancellations and Cachets (GB Overprint Society Study Paper 6) by R. Malim, 1995
Rates and Miscellaneous Matters (GB Overprint Society Study Paper 7) by R Malim, 1993, with revised Part 1 Section A, 1995
Famous and Specialised Auction Catalogues (ordered chronologically)
The Rossi collection of Great Britain Overprints, Warwick & Warwick, 8th June 2005 (prices realised)
Societies
The GB Overprints Society
Journal: The Overprinter
Website: http://www.gbos.org.uk/
The 1887 Jubilee Issue 