Four Parametric Regular Black Hole Solution
  We present a regular class of exact black hole solutions of Einstein equations coupled with a nonlinear electrodynamics source. For weak fields the nonlinear electrodynamics becomes the Maxwell theory, and asymptotically the solutions behave as the Reissner-Nordstr\"om one. The class is endowed with four parameters, which can be thought of as the mass $m$, charge $q$, and a sort of dipole and quadrupole moments $\alpha$ and $\beta$, respectively. For $\alpha \geq 3$, $\beta \geq 4$, and $|q| \leq 2 s_c m$ the corresponding solutions are regular charged black holes. For $\alpha=3$, they also satisfy the weak energy condition. For $\alpha=\beta=0$ we recover the Reissner-Nordstr\"om singular solution and for $\alpha=3$, $\beta=4$ the family includes a previous regular black hole reported by the authors. 
Eloy Ay\'on-Beato and Alberto Garc\'ia