1. Prof., Dept. of Civ. Engrg., Massachusetts Inst. of Tech., Cambridge, MA 02139
2. Infrastructure Systems Analyst, Infrastructure and Urban Development Dept., The World Bank, Washington, D.C.
3. Asst. Prof., School of Civ. Engrg., Purdue Univ., West Lafayette, IN 47907
4. Member of Tech. Staff, AT&T Bell Labs., Holmdel, NJ 07733