The purpose of the following is largely consolidatory. A common basis is provided for the formal relations between forbidden nuclear matrix elements. It is shown how numerical estimates of the coefficients of proportionality can subsequently be made upon introducing on the one hand less on the other hand more detailed nuclear force characteristics. Coarse structure correction factors are derived differing from similar ones appearing in the literature. Finally, it is indicated how theoretical nuclear matrix element ratios may serve in the interpretation of beta spectra.