Não informado. (1968). Professional Engineer. National Society of Professional Engineers.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Professional Engineer. Jersey City, NJ: National Society of Professional Engineers, 1968.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Professional Engineer. National Society of Professional Engineers, 1968.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.