TY  - GEN
AU  - Katharine S Vandoren
C2  - , National Institute of Standards and Technology, Gaithersburg, MD
DA  - 1940-01-01 05:01:00
DO  - https://doi.org/10.6028/NBS.LCIRC.600
LA  - en
PB  - , National Institute of Standards and Technology, Gaithersburg, MD
PY  - 1940
TI  - Letter Circular 600::timekeeping through the ages
ER  -