ABSTRACT
This research was supported by National Science Foundation Grant BNS 8002012 and National Institute of Mental Health Grant MH 34248 to Stanford University. Kathleen Hemenway was supported by a National Science Foundation Fellowship. Portions of this research were reported in a dis.<er..ation by Hemenway in partial fulfillment of the doctorate degree. Kathleen Hemenway is now at Bell Laboratories, Murray Hill, New Jersey.
