Clarke, T., A Catalog Of Philadelphia Postmarks, 18th Century To The Present, Part 1, Domestic Origin Markings, manuscript, handstamp, and machine, 1989, ca. 100 S., Part II, Additional Markings incl. B-O-B origin cancels (ship, foreign, air mail and railroads), received and transit backstamps, and registry postmarks, 1990, ca. 100 S., Part III, Back-of-the-Book Origin Cancels, cont'd, and Auxiliary Markings, incl. Free, Paid, Locals, Meters, Precancels, Undeliverable mail markings, Rollers, Dues, etc., etc., 1992, ca 100 S. 3 Bände komplett, #68811