The Improvement of Estimates of Test Difficulty

Lorge, Irving and Kruglov, Lorraine , "A Suggested Technique for the Improvement of Difficulty Prediction of Test Items". EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT, XII (1952); 554-561.

Tinkelman, Sherman , "Difficulty Prediction of Test Items." Teachers College Contributions to Education, No. 94I. New York, Bureau of Publications, Teachers College, Columbia University, 1947.