TerrellG.Jr., DurkinK., & WiesleyM.Social class and the nature of the incentive in discrimination learning. Journal of Abnormal and Social Psychology, 1959, 59, 270–272.
2.
WarnerW. L., MeekerM. and EellsK.Social class in America.New York: Harper & Row, 1960.
3.
ZiglerE., & deLabryJ.Concept-switching in middle class, lower class and retarded children. Journal of Abnormal and Social Psychology, 1962, 65, 267–273.
4.
ZiglerE., & KanzerP.The effectiveness of two classes of verbal reinforcers on the performance of middle and lower class children. Journal of Personality, 1962, 30, 157–163.