The majority of Field Manuals (FM) within the Library of Congress collections were classed as a serial title. As such these items do not have individual catalog records, hence the need for the inventory, but instead are accessed through the Library of Congress Call number U408.3.A13 followed by a subseries number and date. For example Employment of Aviation of the Army FM 1-5 would be requested as U. S. Dept. of the Army Basic field manual publication U408.3.A13 FM 1-5 Jan. 1943. As the Library of Congress may have more than one version of a manual the month and date is a very important identifier.