Differential Form Approach for Stationary Axisymmetric Maxwell Fields in   General Relativity
  A formulation for stationary axisymmetric electromagnetic fields in general relativity is derived by casting them into the form of an anisotropic fluid. Several simplifications of the formalism are carried out in order to analyze different features of the fields, such as the derivation of electromagnetic sources for the Maxwell field in the form of thin layers, construction of new solutions, and generation techniques. 
L. Fernandez-Jambrina, F.J. Chinea