First Author:   Matthew Jackson California Institute of Technology jacksonm@hss.caltech.edu   HSS 228-77, Caltech Pasadena, 91125, USA       http://www.hss.caltech.edu/~jacksonm/Jackson.html Second Author: Victoria Mason California Institute of Technology vmason@hss.caltech.edu   Humanities and Social Sciences 228-77, California Institute of Technology Pasadena, 91125, USA   626 395 3831(Phone) 626 405 9841(Fax) http://hss.caltech.edu/~jacksonm/SCW.html