Linear NMR in the polar phase of ${}^3$He in aerogel

${}^3$He is an example of the system with non-trivial Cooper paring. A few different superfluid phases are known in this system. Recently the new one, the polar phase, have been observed in ${}^3$He confined in nematically ordered aerogel. A number of various topological defects including half-quantum vortices can exist the polar phase. In this work we present theoretical and numerical studies of linear NMR in the polar phase both in the uniform order-parameter texture and in the presence of half-quantum vortices.