Ehud Weinstein, Meir Feder, and Alan V. Oppenheim.Includes bibliographical references (p. 15).Supported by the Defense Advanced Research Projects Agency, monitored by the Office of Naval Research. N00014-89-J-1489 Supported by the U.S. Air Force Office of Scientific Research. AFOSR-91-0034 Supported by the U.S. Navy Office of Naval Research. N00014-90-J-1109 Supported by the Wolfson Research Awards administered by the Israel Academy of Sciences and Humanities.