TY - GEN AU - Robert E Stephens C2 - , National Institute of Standards and Technology, Gaithersburg, MD DA - 1954-01-01 05:01:00 DO - https://doi.org/10.6028/NBS.CIRC.549 LA - en PB - , National Institute of Standards and Technology, Gaithersburg, MD PY - 1954 TI - Circular of the Bureau of Standards no. 549::computation of achromatic objectives ER -