1. 3Parsons Talcott, and Edward A. Shils , Toward A General Theory of Action , New York: Harper and Row, Publishers, 1951 , pp.19 -20 .
2. 5Robert L. Kahn , Organizational Stress: Studies In Role Conflict and Ambiguity , New York: John Wiley and Sons, Inc., 1964 , p.13 .