TY  - RPRT
TI  - Circular of the Bureau of Standards no. 138: a decimal classification of radio subjects- an extension of the Dewey System
PY  - 1923
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS CIRC 138
DO  - 10.6028/NBS.CIRC.138
ER  -