Inversion of ARPES measurements in high Tc cuprates
  Recent energy dispersion measurements in several families of the hole-doped copper oxides have revealed a kink in the energy vs. momentum relation. These have tentatively been identified as due to electron phonon coupling. We invert this data directly to determine the bosonic spectral function; the kink gives rise to a singular function in the phonon energy region. 
S. Verga, A. Knigavko, and F. Marsiglio