TY  - RPRT
TI  - Letter Circular 485: optical instruments, refractometry, and optical glass: publications (including those in non-governmental periodicals) (superseding Letter Circular 283)
PY  - 1936
PB  - National Institute of Standards and Technology
CY  - Gaithersburg, MD
SN  - LCIRC 485
DO  - 10.6028/NBS.LCIRC.485
ER  -