Não informado. (2002). Principal Leadership. National Association of Secondary School Principals.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Principal Leadership. Reston, Va: National Association of Secondary School Principals, 2002.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Principal Leadership. National Association of Secondary School Principals, 2002.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.