Submodule of free Z-module
Futa, Yuichi, Okazaki, Hiroyuki, Shidama, Yasunari
Higher Order Partial Differentiable Functions
Nakasho, Kazuhisa, Shidama, Yasunari
Definition of Flat Poset and Existence Theorems for Recursive Call
Ishida, Kazuhisa, Shidama, Yasunari, Grabowski, Adam