@article{4731,
  author = {Catharine Garmany and W. Vacca},
  title = {New spectral classifications for O-type stars in the Northern Hemisphere},
  year = {1991},
  journal = {Publications of the Astronomical Society of the Pacific},
  volume = {103},
  pages = {347},
  month = {Jan-08-1991},
  issn = {0004-6280},
  url = {http://articles.adsabs.harvard.edu/full/1991PASP..103..347G},
  doi = {10.1086/132826},
}