Generalization of Regular Black Holes in General Relativity to $f(R)$
  Gravity
  In this paper, we determine regular black hole solutions using a very general
$f(R)$ theory, coupled to a non-linear electromagnetic field given by a
Lagrangian $\mathcal{L}_{NED}$. The functions $f(R)$ and $\mathcal{L}_{NED}$
are left in principle unspecified. Instead, the model is constructed through a
choice of the mass function $M(r)$ presented in the metric coefficients.
Solutions which have a regular behaviour of the geometric invariants are found.
These solutions have two horizons, the event horizon and the Cauchy horizon.
All energy conditions are satisfied in the whole space-time, except the strong
energy condition (SEC) which is violated near the Cauchy horizon.
