Torque through Maxwell Stress Tensor

Dear all:

Recently I tried to implement a similar problem to the one presented in the following poster. The goal is to obtain the force and the torque over a particle that is illuminated by an electromagnetic wave.
www.comsol.com/paper/download/182313/siler_poster.pdf

The force is obtained by integration of the quantity dnTx over a surface that surrounds the particle.
However, I cannot implement the torque because I cannot have access to the Maxwell stress tensor components.
Also I cannot find the quantity dnTx/unTx (upward and downward Maxwell Stress Tensor) in any classical book of electrodynamics (Jackson, Born and Wolf, Landau, Stratton...). I cannot see the difference between quantities. Probably are the projections of the Maxwell stress tensor over the vector perpendicular to the surface, but I would like to confirm this. Thus, it should be exactly the same use dnTx or unTx (except a sign), right?

Can someone help me?
Many thanks in advance.

The expression of the toque is the following:
integral(n \cdot (T x r), surface)
Also is written in the poster cited previously.