TY - CPAPER AU - L. Nelson AU - Judah Levine AU - P. Hetzel CY - Kansas City, MO, USA DA - 2000-06 DO - 10.1109/FREQ.2000.887426 PB - IEEE PP - Kansas City, MO, USA PY - 2000 TI - Comparing primary frequency standards at NIST and PTB ER -