  The strain configuration induced by the lattice mismatch in a core-shell
nanowire is calculated analytically, taking into account the crystal anisotropy
and the difference in stiffness constants of the two materials. The method is
applied to nanowires with the wurtzite structure or the zinc-blende structure
with the hexagonal / trigonal axis along the nanowire, and the results are
compared to available numerical calculations and experimental data. It is also
applied to multishell nanowires, and to core-shell nanowires grown along the
$<001>$ axis of cubic semiconductors.
