Model independent QED corrections to the process $ep \longrightarrow eX$
We give an exhaustive presentation of the semi-analytical approach to the model independent leptonic QED corrections to deep inelastic neutral current lepton-nucleon scattering. These corrections include photonic bremsstrahlung from and vertex corrections to the lepton current of the order ${\cal O}(α)$ with soft photon exponentiation. % A common treatment of these radiative corrections in several variables -- leptonic, hadronic, mixed, Jaquet-Blondel variables -- has been developed and double differential cross-sections are calculated. In all sets of variables we use some structure functions, which depend on the hadronic variables and which do not have to be defined in the quark parton model. The remaining numerical integrations are twofold (for leptonic variables) or onefold (for all other variables). For the case of hadronic variables, all phase space integrals have been performed analytically. Numerical results are presented for a large kinematical range, covering fixed target as well as collider experiments at HERA or LEP$\otimes$LHC, with a special emphasis on HERA physics.