This article is a supplement to the paper of D. A. Dawson and P. March (J.
funet. Anal. 132 (1995), 417-472). We define a two-parameter scale of Banac
h spaces of functions defined on M-1(R-d), the space of probability measure
s on d-dimensional euclidean space, using weighted sums of the classical So
bolev norms. We prove that the resolvent of the Fleming-Viot operator with
constant diffusion coefficient and Brownian drift acts boundedly between ce
rtain members of the scale. These estimates gauge the degree of smoothing p
erformed by the resolvent and separate the contribution due to the diffusio
n coefficient and that due to the drift coefficient. (C) 1998 Academic Pres
s.