1. Listening: Complex of activities—and a unitary skill?
2. Petrie, Charles Robert Jr. 1961. “An Experimental Evaluation of Two Methods for Improving Listening Comprehension Abilities”. 306Purdue University. (unpublished Ph.D. dissertation
3. The effect of a brief training program in listening improvement
4. Gallant, Ruth. 1959. “The Improvement of Listening Comprehension Skills at the College Level”. Oxford, Ohio: Miami University. (unpublished Master's thesis