Susana Muñoz-Hernández Claudio Vaucheret Incomplete Fuzzy Information in Prolog. 787-792 2005 EUSFLAT Conf. http://www.eusflat.org/publications/proceedings/EUSFLAT-LFA_2005/papers/S115-04.pdf conf/eusflat/2005 db/conf/eusflat/eusflat2005.html#Munoz-HernandezV05