@article{gove:logi06,
  author	= {Guido Governatori and Antonio Rotolo},
  title		= {Logic of Violations: A Gentzen System for Reasoning with Contrary-To-Duty Obligations},
  journal	= {The Australasian Journal of Logic},
  year		= 2006,
  volume	= 4,
  pages		= {193-215},
  URL		= {http://www.philosophy.unimelb.edu.au/ajl/2006/},
}