Hawking Radiation from Charged Black Holes via Gauge and Gravitational   Anomalies
  Extending gr-qc/0502074, we show that in order to avoid a breakdown of general covariance and gauge invariance at the quantum level the total flux of charge and energy in each outgoing partial wave of a charged quantum field in a Reissner-Nordstrom black hole background must be equal to that of a (1+1) dimensional blackbody at the Hawking temperature with the appropriate chemical potential. 
Satoshi Iso, Hiroshi Umetsu, Frank Wilczek