Important as it shows with formal proofs how to classify sequences into different levels of difficulty based on computability

comp_sci_fundamentals_and_history/README.md

@@ -5,3 +5,4 @@
 * :scroll: [Back to the Future - The Story of Squeak, A Practical Smalltalk Written in Itself](https://github.com/papers-we-love/papers-we-love/blob/master/comp_sci_fundamentals_and_history/story-of-squeak-a-practical-smalltalk-written-in-itself.pdf) by Dan Ingalls, Ted Kaehler, John Maloney, Scott Wallace & Alan Kay
 * :scroll: [Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I](https://github.com/papers-we-love/papers-we-love/blob/master/comp_sci_fundamentals_and_history/recursive-functions-of-symbolic-expressions-and-their-computation-by-machine-parti.pdf) by John McCarthy
 * :scroll: [An Axiomatic Basis for Computer Programming](https://github.com/papers-we-love/papers-we-love/blob/master/comp_sci_fundamentals_and_history/axiomatic-basis-computer-programming.pdf) by C. A. R. HOARE 
+* :scroll: [On the Computational Complexity of Algorithims](http://www.ams.org/journals/tran/1965-117-00/S0002-9947-1965-0170805-7/S0002-9947-1965-0170805-7.pdf) by J. HARTMANIS AND R. E. STEARNS