@incollection{compref236,
   author = {Meyer,AR and Ritchie,DM},
   year = {1967},
   title = {The Complexity of Loop Programs},
   booktitle = {Proceedings of the 22nd National Conference},
   editor = {   publisher = {Thompson Book Company},
   address = {Washington DC},
   pages = {465-469}
}

@article{compref55,
   author = {Blum,M},
   year = {1967},
   title = {A Machine Independant Theory of the Complexity of Recursive Functions},
   journal = {Journal of the Association of Computing Machinery},
   volume = {14},
   pages = {322}
}

@incollection{compref38,
   author = {Bar-Hillel and Kasher,Y and Shamir,E},
   year = {1967},
   title = {Measures of Syntactic Complexity},
   booktitle = {Machine Translation},
   editor = {Booth,AD},
   publisher = {North-Holland},
   address = {Amsterdam},
   pages = {30-50}
}