  We derive the evolution equations of parton distribution functions
appropriate in different kinematic regions in a unified and simple way using
the resummation technique. They include the
Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation for large momentum transfer
$Q$, the Balitskii-Fadin-Kuraev-Lipatov equation for a small Bjorken variable
$x$, and the Ciafaloni-Catani-Fiorani-Marchesini equation which embodies the
above two equations. The relation among these equations is explored, and
possible applications of our approach are proposed.
