The structure functions and parton momenta distribution in the hadron   rest system
  The alternative to the standard formulation of QPM in the infinite momentum frame is suggested. The proposed approach does not require any extra assumptions in addition, consistently takes into account the parton transversal momenta and does not prefer any special reference system. The standard approach is involved as a limiting case. In the result the modified relations between the structure and distribution functions are obtained together with some constraint on their shape. The comparison with experimental data offers a speculation about values of effective masses of quarks, which emerge as a free parameter in the approach. 
P. Zavada