The United States Postage Stamps of the 20th Century Volumes II & III 1st Ed.,1934, 1935.  Volume 2 is by Beverly S. King and Max G. Johl and features the commemoratives from 1923-1933 and Volume 3 by Max G. Johl features Airmail and Parcel Post stamps from 1922-1934. These are fabulous volumes loaded with info and history and many great photographs.