The Standard Model and Fermion Masses
  The paper formulates the Standard Model with massive fermions without introduction of the Yukawa interaction of Higgs bosons with fermions. For invariance to be preserved in the newly stated theory, the covariant derivative should be generalized, as follows. With such approach, Higgs bosons are responsible only for the gauge invariance of the boson sector of the theory and interact only with gauge bosons, gluons and photons. 
V.P. Neznamov