Sheppard and Kemp differently identified the difference between canonical (Minkowski) and kinetic (Abraham) momenta, explaining that the canonical momentum or wave momentum "represents the combination of both field and material momentum values", while the kinetic momentum "represents the photon momentum void of material contributions". This explanation is completely consistent with Alexander Feigel's finding that "Abraham's expression is indeed the momentum of the field, the measured momentum also includes the matter contribution, and its value coincides with Minkowski's result"; thus "the Abraham definition accounts for the momentum of the electric and magnetic fields alone, while the Minkowski definition also takes into account the momentum of the material". According to this theory, Abraham momentum formula_6 is the quantized field momentum (= field part of total momentum/photon number), while the Minkowski momentum formula_3 is the quantized wave momentum (= total momentum including both field part and material part/photon number).