1. “The Reference Assessment Manual”,1995
2. Information Service in Public Libraries; Two Studies;Crowley,1971
3. “Unobtrusive Reference Testing: The 55 Percent Rule”;Hernon;Library Journal,1986
4. “Reference Success: Does the 55 Percent Rule Tell the Whole Story?”;Durrance;Library Journal,1989
5. “Flying a Light Aircraft: Reference Service Evaluation from a User Viewpoint”;Dewdney;RQ,1994