How can I find a microfilm that I know I used before if I do not have its call number?
Nearly all microform call numbers can be found in CLIO.
If the microform is not listed in CLIO, the call number can be found in the Periodicals & Microforms Reading Room (PMRR) card catalog.
Indexes may have to be used in conjunction with a call number to identify specific dates, series numbers, reel numbers, etc. See also Indexes to Major Microform Collections at PMRR.