I mean you have the groups (6. and 7.) from there you get all the variables. E.g. from U(1) you get the generator and the group item. Then add all combinations of the polynomes to L (1.) but skip those that violate invariances like Lorentz (2.), U(1), SU(2), SU(3). You end up with something like L=-1/2 d phi^2 - m phi^2. (Oversimplified) Do the same for SU(2) and SU(3) and you end up with http://nuclear.ucdavis.edu/~tgutierr/files/sml2.pdf For convenience usually some of the variables are then called e (Electron), W+ (W+ Boson) etc.