To obtain a NASA report published prior to 1995 obtain the NASA Accession Number (e.g. N75-17011) , then locate the file cabinet, drawer and search by consecutive numbers.
NASA reports published from 1996 on are filed by SERIES. Series include:
These are filed alphabetically first by the full series name if abbreviated ( i.e. NASA-Case, NASA-CP, NASA-CR, NASA-EP, NASA-RP, NASA-SP, NASA-TM, NASA-TN etc), then by the year of publication, if present, and finally by the NASA Record Number.
To search for NASA-Technical Memorandum-50734: Look under NASA-TM-50734, and also under NASA-TM-[Year]-50734 or NASA-Technical Memorandum-1998-50734. The YEAR, if present, may be represented as two or four digits.