TY  - RPRT
TI  - Frequency standards and clocks : a tutorial introduction (revised edition)
AU  - Hellwig, Helmut
PY  - 1972
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS TN 616r1
DO  - 10.6028/NBS.TN.616r1
ER  -