連続数学でやってきたので離散数学は苦手なんだけど，有限の特許期間など微分差分方程式を解くなど，離散系も奥深そう。
有限の特許期間はLin and Shampine (2018)が the patent length does not essentially matter with respect to endogenous growth (or at least its qualitative properties)と結論付けてからはまあ良いかなって感じ。
Lin, H.C., Shampine, L.F., (2018) "R&D-based calibrated growth models with finite-length patents: A novel relaxation algorithm for solving an autonomous FDE systems of mixed type" Computational Economics 51, 123?158
