Stress/atom formula

I am studying the calculation of "stress on each atom" of the system. I'm trying to understand the formula to compute stress/atom like in the help (with the book "Modeling Materials - continuum, atomistic and multiscale techniques", in 2011, Cambrigde Presse) but it is not easy to understand everything. Could someone advise me some book or paper that explain better?

You can look at the J Chem Phys paper by A Thompson on
the citations page of the LAMMPS web site.