Theorem $f \in \mathrm{C} (\mu \circ \mu^{- 1} ; \nu \circ \nu^{- 1}) \Leftrightarrow f \in \mathrm{C} (\mu; \nu)$ for complete endofuncoids $\mu$, $\nu$ and principal monovalued and entirely defined funcoid $f \in \mathsf{FCD} (\mathrm{Ob}\, \mu; \mathrm{Ob}\, \nu)$, provided that $\mu$ is reflexive, and $\nu$ is $T_1$-separable.
Here $f \in \mathrm{C} (\mu; \nu)$ means that $f$ is a continuous morphism from a “space” $\mu$ to a “space” $\nu$.