@inproceedings{NSS08,
author = {S. Nieva and F. {S\'aenz-P\'erez} and J. S\'anchez},
title = {{Formalizing a Constraint Deductive Database Language based on Hereditary Harrop Formulas with Negation}},
    booktitle = {Proc. 9th International Symposium on Functional and Logic Prrogramming (FLOPS'08)},
    year = {2008},
    publisher = {Springer Verlag},
    series = {LNCS},
    volume = {4989},
    pages = {289--304}
}