Paper  bibtex   

@article{ caines_hierarchical_1998,
  title = {Hierarchical hybrid control systems: A lattice theoretic formulation},
  volume = {43},
  shorttitle = {Hierarchical hybrid control systems},
  url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=664153},
  number = {4},
  urldate = {2013-09-24},
  journal = {Automatic Control, {IEEE} Transactions on},
  author = {Caines, Peter E. and Wei, Yuan-Jun},
  year = {1998},
  pages = {501–508}
}