TY - GEN AU - Petty, Eyvon M C2 - , National Institute of Standards and Technology, Gaithersburg, MD DA - 2009-01-01 05:01:00 DO - https://doi.org/10.6028/NIST.IR.6656-08 LA - en PB - , National Institute of Standards and Technology, Gaithersburg, MD PY - 2009 TI - NIST time and frequency bulletin, no. 620: ER -