Two-loop master integrals for $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ process with account of electron mass

We calculate a subset of two-loop master integrals relevant for the differential cross section of $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ process. We consider only those families for which the account of the electron mass $m$ is necessary. Our results have the form of the Frobenius series in $m$ with coefficients expressed via Goncharov’s polylogarithms.