Francesco Calimeri Susanna Cozza Giovambattista Ianni External sources of knowledge and value invention in logic programming. 333-361 2007 50 Ann. Math. Artif. Intell. 3-4 http://dx.doi.org/10.1007/s10472-007-9076-z db/journals/amai/amai50.html#CalimeriCI07