Alireza Tamaddoni-Nezhad Stephen Muggleton A Note on Refinement Operators for IE-Based ILP Systems. 297-314 2008 ILP http://dx.doi.org/10.1007/978-3-540-85928-4_23 conf/ilp/2008 db/conf/ilp/ilp2008.html#Tamaddoni-NezhadM08