1. Gray, R. T. “An Evaluation of the Effect of an Immediate Feedback Device Used with Typical College Classroom Tests,” ERIC, BR-6-8156-015-658, 1968.
2. Heald, H. M. “The Effects of Immediate Knowledge of Results and Correlation of Errors and Text Anxiety upon Test Performance,” doctoral dissertation, University of Nebraska, University Microfilms, Ann Arbor, Michigan, No. 70-17:724, 1970.