TY  - RPRT
TI  - Letter Circular 499: the weekly radio broadcasts of the National Bureau of Standards on the ionosphere and radio transmission conditions
PY  - 1937
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 499
DO  - 10.6028/NBS.LCIRC.499
ER  -