1. Projections instead of variables, a category theoretic interpretation of logic programs;Asperti,1989
2. Term graph reduction;Barendregt,1987
3. Graph expressions and graph rewritings;Bauderon;Math. Systems Theory,1987
4. PROLOG II - Reference Manual and Theoretical Model;Colmerauer,1982
5. Logic programming and graph grammars;Corradini,1991