The python script "problem-68.py" can be used to check the most
tedious calculations of 68.c and 68.d


It involves the following steps:

- Calculation P_\mu P^\mu
- Calculation of the numerator and denominator of Sum_{cuts} 2*(s_34 epsilon(123,l3)-s_12 epsilon(l3,234))/(p4.l3)


To run the script (inside a jupyter console), do:
    load "problem-68.py"


The output of the script is included in the file "output.txt"
