"Ryo Kashima,Takeshi Yamaguchi","On the Difficulty of Writing Out Formal Proofs in Arithmetic",,"Mathematical Logic Quarterly",,"Vol. 43",,"pp. 328-332",1997, "RYO KASHIMA","Contraction-Elimination for Implicational Logics",,"Annals of Pure and Applied Logic",,"Vol. 84",,"pp. 17-39",1997, "田中一之,鹿島亮,角田法也,菊池誠","数学基礎論講義-不完全性定理とその発展",,"日本評論社","日本評論社",,,,1997,