  The accuracy of the vacuum saturation hypothesis is discussed using the
examples of vacuum expectation values of four-quark operators and the parameter
$B$, which determines the short-distance contribution to the $K^0 - \bar K^0$
mixing. Note added: The approach based on sum rules in position (x-)space as
elaborated in the paper is relevant and useful tool for the current
phenomenology. In particular, it provides the unique possibility of direct
non-perturbative estimation of the VEV's of four-quark operators renormalized
in any scheme, including the MSbar one.
