Kenzi Watanabe Teisuke Yamaguchi Hiroyuki Egashira Joe Ito Yasuhisa Okazaki Hiroki Kondo Masayoshi Okamoto Takatoshi Yoshikawa FRONTIER: An Application of A Pen Based Interface to An ITS For Guiding Fraction Calculation. 238-242 1999 conf/hci/1999-1 HCI (1) db/conf/hci/hci1999-1.html#WatanabeYEIOKOY99