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Dyfyniad Arddull ChicagoDeVellis, Robert F. Scale Development: Theory and Applications. Newbury Park, Calif.: Sage, 1991.
Dyfyniad MLADeVellis, Robert F. Scale Development: Theory and Applications. Sage, 1991.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.