Paqui Lucio Fernando Orejas Edelmira Pasarella Elvira Pino A Functorial Framework for Constraint Normal Logic Programming. 421-450 2008 16 Applied Categorical Structures 3 http://dx.doi.org/10.1007/s10485-008-9128-5 db/journals/acs/acs16.html#LucioOPP08