Fernando Orejas Edelmira Pasarella Elvira Pino Semantics of Normal Logic Programs with Embedded Implications. 255-268 2001 conf/iclp/2001 ICLP http://link.springer.de/link/service/series/0558/bibs/2237/22370255.htm db/conf/iclp/iclp2001.html#OrejasPP01