NTCIR-2 Experiments Using Long Gram Based Indices. - Takashi Sato 005; Nao Hatta; Koji Hiraiwa; Kihei Kobata; Akihiro Furusho; Koto Han (NTCIR, 2001)

NTCIR-4 PATENT Experiments at Osaka Kyoiku University - Gram-Based Passage Index and Essential Words. - Takashi Sato 005; Nao Hatta (NTCIR, 2004)