Calculation of a weak nonleptonic matrix element using ``Weinberg'' sum   rules
  There is a ``toy'' weak matrix element which can be expressed as an integral over the vector and axial vector spectral functions, $\rho_V (s) - \rho_A (s)$. I review our recent evaluation of these spectral functions, the study of four ``Weinberg'' sum rules and the calculation of this matrix element. 
John F. Donoghue