We deal with equations on post-composition of holomorphic functions on the open unit disk under the condition that quotients of de Branges-Rovnyak kernels are positive semi-definite.
Dedicated to Professor Osamu Hatori on the occasion of his retirement.
"Quotients of kernel functions and post-composition." Nihonkai Math. J. 31 (1) 1 - 5, 2020.