  The rate for the production of massive fermions radiated off a pair of
massless fermions is calculated analytically. Combined with the analytic
calculation of the corresponding virtual contribution one obtains the order
$\alpha^2$ correction to the cross section which is induced by the real and
virtual radiation of a pair of massive fermions by massless fermions.
Approximations valid for large and for small masses are derived and shown to
agree with earlier calculations.
