TY  - RPRT
TI  - Letter Circular 591: standards of frequency and musical pitch broadcast by National Bureau of Standards (replaces Letter Circular 565)
PY  - 1940
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 591r1940
DO  - 10.6028/NBS.LCIRC.591r1940
ER  -