  In this note we present variants of Kostov's theorem on a versal deformation
of a parabolic point of a complex analytic $1$-dimensional vector field. First
we provide a self-contained proof of Kostov's theorem, together with a proof
that this versal deformation is indeed universal. We then generalize to the
real analytic and formal cases, where we show universality, and to the
$C^\infty$ case, where we show that only versality is possible.
