Não informado. (1999). Shools in the middle. National Association of Secondary School Principals.
Chicago-referens (17:e uppl.)Não informado. Shools in the Middle. Reston, Va: National Association of Secondary School Principals, 1999.
MLA-referens (8:e uppl.)Não informado. Shools in the Middle. National Association of Secondary School Principals, 1999.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.