The name of the authoritative list for a controlled value is recorded here.
Gateway to Educational Materials (GEM) Level Element Controlled Vocabulary
GEM CV is: Higher education; Adult/Continuing education
LC Educational Sectors, as cited in PBCore [http://www.pbcore.org/PBCore/picklists/picklist_audienceLevel.html]
LC Educational Sectors CV is: K-12 (general); Pre-school (kindergarten); Primary (grades 1-6); Intermediate (grades 7-9); High School (grades 10-12); College; Post Graduate; General Education; Educator; Vocational; Adult; Special Audiences; General; Male; Female; Other
Motion Picture Association of America (MPAA)
MPAA CV is: G; PG; PG-13; R; NC-17; NR