TY  - RPRT
TI  - Letter Circular 554: electrical measuring instruments, meters and their accessories (superseding Letter Circular 364 and 233)
PY  - 1939
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 554
DO  - 10.6028/NBS.LCIRC.554
ER  -