TY  - RPRT
TI  - Letter Circular 534: commercial testing laboratories equipped for chemical analysis (supersedes Letter Circular 196)
PY  - 1938
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 534
DO  - 10.6028/NBS.LCIRC.534
ER  -