TY  - RPRT
TI  - Letter Circular 540: artificial abrasives and abrasive products (replaces Letter Circular 527)
PY  - 1938
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 540
DO  - 10.6028/NBS.LCIRC.540
ER  -