@article{humb:moda08,
  author	= {Lloyd Humberstone},
  title		= {Modal Formulas True at Some Point in Every Model },
  journal	= {The Australasian Journal of Logic},
  year		= 2008,
  volume	= 6,
  pages		= {70--82},
  URL		= {http://www.philosophy.unimelb.edu.au/ajl/2008/},
}