Hidenobu Kunichika Minoru Urushima Tsukasa Hirashima Akira Takeuchi A Computational Method of Complexity of Questions on Contents of English Sentences and its Evaluation. 97-101 2002 ICCE db/conf/icce/icce2002-1.html#KunichikaUHT02 http://doi.ieeecomputersociety.org/10.1109/CIE.2002.1185873