etail and ptail Formalism?

It's a part of the born, buck, lj, and lj96 pair_styles. Where can I read about the formulation from the potential energy functions?

Thanks again!
-Mike W.

The pair_modify doc page gives formulas from a cited ref.
Or you can look in the source code for those files. Search
for "tail" and you will find the handful of code lines that
implement it.