Hello! I am trying to construct (if it is possible) a potential formulation of an electromagnetic theory which permits the presence of magnetic sources, using as a starting point the equations refered here: http://en.wikipedia.org/wiki/Magnetic_monopole Although I think that I have make some progress, I would like to know if there is such a theory already. Does anybody has something in mind? If the answer is negative, I would also like to know if there is some particular reason why such a theory cannot not exist. Thank's in advance!