\[\rselection{{H^{(1)}_{\nu}}\left(z\right)\\
{H^{(2)}_{\nu}}\left(z\right)}=\mp 2\pi^{-\frac{1}{2}}ie^{\mp\nu\pi i}(2z)^{%
\nu}\*e^{\pm iz}U\left(\nu+\tfrac{1}{2},2\nu+1,\mp 2iz\right).\]