Submodule of free Z-module
Futa, Yuichi, Okazaki, Hiroyuki, Shidama, Yasunari
Isometric Differentiable Functions on Real Normed Space
Futa, Yuichi, Endou, Noboru, Shidama, Yasunari
Isomorphism between Spaces of Multilinear Maps and Nested Compositions over Real Normed Vector Spaces
Nakasho, Kazuhisa, Futa, Yuichi