A theory of the process of change / by Irwin Bernhardt and Kenneth D. Mackenzie.
- Philadelphia, Pa. : Dept. of Industry, Wharton School of Finance & Commerce, University of Pennsylvania, 
43 leaves : ill. ; 28 cm.
- Working paper (Wharton School. Dept of Industry) ; no. 78.
Working paper / Dept. of Industry, Wharton School of Finance & Commerce, University of Pennsylvania ; no. 78