@book{compref56,
   author = {B”rger,E},
   year = {1989},
   title = {Computability, Complexity, Logic},
   publisher = {North Holland},
   address = {Amsterdam}
}

@article{compref2,
   author = {Aaderaa,SO and B”rger,E},
   year = {1981},
   title = {The equivalence of Horn and network complexity of Boolean functions},
   journal = {Acta Informatica},
   volume = {15},
   pages = {303-307}
}

@incollection{compref1,
   author = {Aaderaa,SO and B”rger,E},
   year = {1979},
   title = {The Horn Complexity of Boolean functions and Cook's problem},
   booktitle = {Proceedings of the 5th Scandanavian Logic Symposium},
   editor = {Mayoh,B and Jensen,F},
   publisher = {Aalborg University Press},
   address = {Aalborg},
   pages = {231-256}
}