Ship mail including North Atlantic Mail Sailings 1840-1875 by W. Hubbard and R.F. Winter (1988, limited Special Edition of 25 (this is no. 16)), The History of the Sailing Packets to the West Indies by L.E. Britnor (1973), The Private Ship Letter Stamps of the World by H.B. d'Humières, S. Ringström and H.E. Tester (1976, 3 parts and 2 duplicates), Paquebot and Ship Letter Cancellations of the World 1894-1951 by M.A. Studd (1953),
