Joxe Gaintzarain Montserrat Hermo Marisa Navarro Goals in the Propositional Horn Language Are Monotone Boolean Circuits. 376-386 2005 conf/mfcs/2005 MFCS http://dx.doi.org/10.1007/11549345_33 db/conf/mfcs/mfcs2005.html#GaintzarainHN05