De Souto, M. S. (1985). Group travel operations manual. Delamr Pub.
Chicago Style aipamenaDe Souto, Martha Sarbey. Group Travel Operations Manual. Albany, N.Y: Delamr Pub, 1985.
MLA aipamenaDe Souto, Martha Sarbey. Group Travel Operations Manual. Delamr Pub, 1985.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.