TY  - RPRT
TI  - Letter Circular 503: propane, butane, and related fuels (supersedes Letter Circular 292)
PY  - 1937
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 503
DO  - 10.6028/NBS.LCIRC.503
ER  -