Makoto Haraguchi Yoshiaki Okubo Tokuyasu Kakuta A Logical Foundation of Metaphoric Search Based on Abstraction Approach. 53-81 2000 4 Electron. Trans. Artif. Intell. B http://www.ep.liu.se/ej/etai/2000/010/ db/journals/etai/etai4.html#HaraguchiOK00