Symmetry Considerations for the Detection of Second-Harmonic Generation   in Cuprates in the Pseudogap phase
  A proposal to test the proposed time-reversal and inversion breaking phase in the Pseudogap region of the Cuprate compounds through the variation of Second-harmonic generation intensity with temperature and polarization and angle of incidence is presented. 
M. E. Simon and C. M. Varma (Bell Laboratories, Lucent Technologies)