TY - CONF AU - Thomas Parker AU - David Howe AU - Marc Weiss C2 - 1998 Intl. Freq. Cont. Symp. , Pasadena, CA DA - 1998-01-01 LA - en PB - 1998 Intl. Freq. Cont. Symp. , Pasadena, CA PY - 1998 TI - Accurate Frequency Comparisons at the 1 {?} 10-15 Level ER -