1. Prof., Mechanics Div., Catholic Univ. of America, Washington, D. C.
2. Universidad Nacional de Ingenieria, Lima, Peru; formerly, Research Assoc., Mechanics Div., Catholic Univ. of America, Washington, D. C.
3. Asst. Prof., Mechanics Div., Catholic Univ. of America, Washington, D. C.
4. Research Assoc., Mechanics Div., Catholic Univ. of America, Washington, D. C.