@misc{1191316,
  author = {Robert E Stephens},
  title = {Circular of the Bureau of Standards no. 549::computation of achromatic objectives},
  year = {1954},
  month = {1954-01-01 05:01:00},
  publisher = {, National Institute of Standards and Technology, Gaithersburg, MD},
  doi = {https://doi.org/10.6028/NBS.CIRC.549},
  language = {en},
}