These files show how to derive Eq. A5 of the paper.


We move towards 2PN_et_1.nb >> 2PN_et_3.nb >> 2PN_et_5.nb, we gradually obtain expressions of e_t which is more and
more accurate in orders of e_0. The outputs of the lower order file serve as the inputs to the next higher order
file.


Out of 2PN_et_1.nb serves as input to 2PN_et_3.nb.