* [Purely Functional Lazy Non-deterministic Programming](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.148.524)
* :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)