$\varepsilon_{\perp}^{eff}$, $\varepsilon_{\parallel}^{eff}$ are very *different from the bulk values* in $SrTiO_{3}$ (in $1ML$ $FeSe/TiO_{2}$ one has $\varepsilon\leq260$ [@Rebec-FeSe-TiO2]). This is physically plausible since for the nearest (to the $FeSe$ monolayer) $TiO_{2}$ dipolar monolayer there is almost nothing to screen in the direction perpendicular to $FeSe$, thus making $\varepsilon
_{\perp}^{eff}\ll$ $\varepsilon^{bulk}$. Note, that for the parameters assumed in this analysis and for $T_{c0}\approx100$ $K$ one obtains rather large bare pairing potential $V_{epi}^{0}\approx10$ $eV$ . This means that in the absence of the $FSP$ in $EPI$ and for the density of states of the order $N(E_{F})\sim0.5$ $(eV)^{-1}$ (typical for Fe-based superconductors) the bare coupling constant $\lambda_{epi}^{0}=N(E_{F})V_{epi}^{0}$ would be large, $\lambda_{epi}^{0}\sim5$. We stress that the above theory is also applicable to recently discovered $1ML$ $FeSe/TiO_{2}$ [@Rebec-FeSe-TiO2]. To conclude, the high $T_{c0}$ in $1ML$ $FeSe/SrTiO_{3}$ (and $1ML$ $FeSe/TiO_{2}$) is obtained on the expense of the large maximal $EPI$ coupling $V_{epi}^{0}$ which compensates smallness of the (detrimental) phase-volume factor $(aq_{c})^{2}$.

Effects of impurities on $T_{c0}$
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In clean systems with the $EPI-FSP$ mechanism of superconductivity $T_{c0}$ is degenerate - it is equal in $s$- and $d$-channels. In the following we show, that the $s$-wave superconductivity is also affected by isotropic non-magnetic impurities, i.e. $T_{c0}$ is 