  The correlators of light-quark currents contain mass-singularities of the
form log(m^2/Q^2). It has been known for quite some time that these mass-
logarithms can be absorbed into the vacuum expectation values of other
operators of appropriate dimension, provided that schemes without normal-
ordering are used. We discuss in detail this procedure for the case of the mass
logarithms m^4 log(m^2/Q^2), including also the mixing with the other
dimension-4 operators to two-loop order. As an application we present an
improved QCD sum rule determination of the strange-quark mass. We obtain m_s(1
GeV)=171 \pm 15 MeV.
