Matsuda, Noriyuki, Hisashi Ogawa, Tsukasa Hirashima, and Hirokazu Taki. 2015. “A Generating Technique and Knowledge Representation of Multiple-Answer Problems for Learning With Solving Knowledge”. Research and Practice in Technology Enhanced Learning 10 (June). https://rptel.apsce.net/index.php/RPTEL/article/view/2015-10006.