@misc{oai:chuo-u.repo.nii.ac.jp:00001104,
 author = {MITSUMATSU, Yoshihiko and KODAMA, Hiroki and MASUDA, Kazuo},
 month = {Apr},
 note = {application/pdf, We remark that there is no smooth function f (x) on [0, 1] which is flat at 0 such that the derivative f^ (n) of any order n≧0 is positive on (0, 1]. Moreover, the number of zeros of the n-th derivative f^ (n) grows to the infinity and the zeros accumulate to 0 when n → ∞.},
 title = {Derivatives of flat functions},
 year = {2018}
}