Universal Weak Lensing Distortion of Cosmological Correlation Functions
  Gravitational lensing affects observed cosmological correlation functions because observed images do not coincide with true source locations. We treat this universal effect in a general way here, deriving a single formula that can be used to determine to what extent this effect distorts any correlation function. We then apply the general formula to the correlation functions of galaxies, of the 21-cm radiation field, and of the CMB. 
Scott Dodelson, Fabian Schmidt, Alberto Vallinotto