TY  - RPRT
TI  - Letter Circular 513: sources of radio information (replaces Letter Circular 474)
PY  - 1938
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 513r1938
DO  - 10.6028/NBS.LCIRC.513r1938
ER  -