Yang's catalogue is one of the three stamp catalogues published by Yang's Stamp Service of Hong Kong:
To correlate Wang catalog numbers and Scott catalogue numbers for Hong Kong consult Hong Kong Scott-Yang Catalog Correlation by Ralph Weil with Michael Rogers. 2006, second edition. To correlate Wang catalog numbers and Scott catalog numbers for the People's Republic of China consult Scott-Yang/Yang-Scott Catalog Correlation of the Peoples Republic of China (Liberated and Unified Areas) edited by Ralph Weil with Michael Rogers. 2006, Softbound, second edition. To correlate Wang catalog numbers and Scott catalog numbers for the Macau consult Macau Scott-Yang/Yang-Scott Catalog Correlation by Ralph Weil with Michael Rogers. 2006, second edition.
Although the Liberated Area (Communist local issues from 1930-1950) catalogue is now quite old, it is still considered the best existing catalogue of this specialised area.