We are grateful for the assistance of many people who have contributed to this project, including Rolando Zeledon, Bayle Shanks, Kent Koth, Art McGee, Sally Kiester, Laurence of Berkeley, and David Taylor. This work was funded by a Public Scholarship Initiative grant from the Vice Provost for Undergraduate Education (VPUE) at Stanford administered by the Hass Center for Public Service, by a VPUE Departmental Grant to the Symbolic Systems Program, and an unrestricted gift to the Symbolic Systems Program by Ric Weiland.