David G. Phillips · UMI Books on Demand
| title | ISBN-13 (ISBN-10) | year of publication |
|---|---|---|
| A Collector's Guide to U.S. Machine Postmarks, 1871-1925, with Examples of Later Types | 978-1-877998-04-1 (1-877998-04-4) | 1998 |
| A Collector's Guide to U.S. Machine Postmarks 1871-1925 With Examples of Later Types | 978-0-318-03728-8 (0-318-03728-9) | 1990 |