  Techniques for using Gaussian QCD sum-rules to predict hadronic resonance
properties are developed for single-resonance and two-resonance
phenomenological models, and criteria are developed for determining which of
these models is required for analyzing a particular hadronic channel. The
vector current sum-rule coupled to the $\rho$ meson is shown to be consistent
with a single resonance model, and the Gaussian sum-rule analysis results in an
accurate $\rho$ mass prediction which exhibits excellent agreement between the
theoretical prediction of the Gaussian sum-rule and the phenomenological model.
A two-resonance model is shown to be necessary for the Gaussian sum-rule for
the non-strange quark scalar ($\bar n n$) currents. The two-resonance Gaussian
sum-rule analysis of the isoscalar and isovector ($I=0,1$) $\bar n n$ scalar
mesons exhibits excellent agreement between the theoretical prediction and
phenomenological model. The prediction of the resonance properties of the
$I=0,1$ $\bar n n$ scalar mesons in this two-resonance model provides valuable
information for the interpretation of the scalar mesons, including the X(1775).
