Não informado. (1926). Bulletin of the National Association of Secondary School Principals. National Association of Secondary School Principals.
Citação do estilo Chicago (17ª ed.)Não informado. Bulletin of the National Association of Secondary School Principals. Washington: National Association of Secondary School Principals, 1926.
Citação MLA (8ª ed.)Não informado. Bulletin of the National Association of Secondary School Principals. National Association of Secondary School Principals, 1926.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.