On the origin of current quark mass within nonperturbative QCD
  We develop the theory of fermion induced phononlike excitations of the instanton liquid. It suggests a mechanism of current quark mass generation which is easily understandable by calculating the corresponding functional integral in the tadpole approximation. We systematically study the quark condensate excitations influenced by the phononlike modes and rederive the relation Gell-Mann-Oakes-Renner with realistic pion mass. The picture of $\sigma$-meson as being mixed with the soft scalar glueball-like excitation is discussed. 
S.V. Molodtsov, A.M. Snigirev, G.M. Zinovjev