  Within the global setting of singular drifts in Morrey-Campanato spaces
presented in [6], we study now the H{\"o}lder regularity properties of the
solutions of a transport-diffusion equation with nonlinear singular drifts that
satisfy a Besov stability property. We will see how this Besov information is
relevant and how it allows to improve previous results. Moreover, in some
particular cases we show that as the nonlinear drift becomes more regular, in
the sense of Morrey-Campanato spaces, the additional Besov stability property
will be less useful.
