TY - CONF AU - Thomas Heavner AU - Steven Jefferts AU - Elizabeth Donley AU - Jon Shirley AU - Thomas Parker C2 - 2004 IEEE Conf. on Precision Electromagnetic Measurements , London, UK DA - 2004-01-01 LA - en PB - 2004 IEEE Conf. on Precision Electromagnetic Measurements , London, UK PY - 2004 TI - Recent Improvements In NIST-F1 and Resulting Accuracies of δf/f<7 {?}10-16, ER -