Literature
Oil Rivers and Niger Coast Protectorates by F. J. Melville, 1924
The Local Bisects and Surcharges of the Oil Rivers and Niger Coast 1893 – 1894 (Cockrill Series Booklets no. 30) by M. P. Nicholson
The Postal Services of the British Nigeria Region by Ince and Sacher, 1992
Niger Coast Provisionals 1893 by Warwick & Warwick, 2005
Famous and Specialised Auction Catalogues (listed in chronological order)
Pilkington, G. L., Robson Lowe, 1954
Rossi collection of Great Britain Overprints, Warwick & Warwick, 8th June 2005
The 1887 Jubilee Issue 