sentences:  Because of the complexity involved with these stamps the organization below of these issues is motivated by making the identification of these issues as simple as possible for people who are not yet familiar with these stamps.Chan recognises 26 separate Sun Yat-sen definitive issues up to 1949, including provincial issues, and is perhaps the most logical and rigorous of the China stamp catalogues in this area.The first Sun Yat-sen definitives were issued in 1931, and were recess printed by De La Rue & Co. of London.