@article
{ClearyLu98,
author ={J.G. Cleary and L. Lu},
title = {Constructive Negation Using Typed Existence Properties},
journal = {Lecture Notes in Computer Science},
volume = 1490,
pages = {411-426},
year = 1998,
keywords = {Types, Constructive Negation},
url = {http://www.oakland.edu/~l2lu/pubs/CN.ps}
}