For specific subject searches of LC, MeSH, and NASA subject headings, the wildcard character, "?" (question mark) must be used if the exact heading is unknown. For example:
LC heading search of libraries retrieves only records with "libraries" as a subject heading.
LC heading search of libraries? also retrieves records in which "libraries" is only the first element of the subject heading, e.g., "libraries - security measures"
super? = super, superconductor, superintendent, superpower, supervisory, etc.