* [Purely Functional Lazy Non-deterministic Programming](http://www.cs.rutgers.edu/~ccshan/rational/lazy-nondet.pdf)
* :scroll: [On the Meanings of the Logical Constants and the Justifications of the Logical Laws](http://www.pps.univ-paris-diderot.fr/~saurin/Enseignement/LMFI/articles/Martin-Lof83.pdf)