Go to \caesarii\c2_docu and open "c2tr.pdf". ("caesarii" is your installation directory.) Once the PDF is open, navigate to page 6-85 and 6-86.

You also need to reference one of the FRP data files located in \caesarii\system - I suggest "wavin73.frp". Open this with a text editor, such as NotePad. The 'sigma' values defining the interaction curve are located at the bottom of the file.