Laws' Index was a monumental work, but probably of very little use to anyone. He classified broadside ballads in a hierarchical scheme, where an initial letter designated the general category (Murder, Marriage, Negro etc.) and a number to identify the particular song. Problem is, it doesn't work for a Negro murder ballad, f'rinstance, where more than one category may apply. Laws also didn't provide examples in his index, and his references are often unobtainable, so that it's impossible to determine the logic of listings like: Plains of Waterloo I , Plains of Waterloo II, etc.

In a smaller, though IMO still monumental effort towards clarifying Laws' Index, Susan of DT spent a good deal of time tracking down an example of each of the Laws-numbered ballads and added them, with Laws Numbers, to digiTrad.