Comments on the dependence between electric charge and magnetic charge
  By using the two 4-dimensional potential formulation of electromagnetic (EM) field theory introduced in [1], we found that the SO(2) duality symmetric EM field theory can be reduced to the magnetic source free case by a special choice of SO(2) parameter,this special case we called nature picture of the EM field theory, the reduction condition led to a result, i.e. the electric charge and magnetic charge are no more independent. Some comments to paper [SD] are also mentioned. 
Kang Li