@article{compref339,
   author = {Walker,CC},
   year = {1971},
   title = {Behaviour of a Class of complex systems: The effect of systems size on properties of terminal cycles},
   journal = {Journal of Cybernetics},
   volume = {1},
   pages = {55-67}
}

@misc{compref697,
   author = {Van Emden,MH},
   year = {1971},
   title = {An Analysis of Complexity},
   howpublished = {Mathematical Centre Tracts, Mathematisch Centrum Amsterdam, Amsterdam, 1971}
}

@article{compref26,
   author = {Ausiello,G},
   year = {1971},
   title = {Abstract Computational Complexity and Cycling Computations},
   journal = {Journal of Computer and System Sciences},
   volume = {5},
   pages = {118-128}
}