TY  - RPRT
TI  - Circular of the Bureau of Standards no. 549: computation of achromatic objectives
AU  - Stephens, Robert E
PY  - 1954
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS CIRC 549
DO  - 10.6028/NBS.CIRC.549
ER  -