Region unknotting number of $2$-bridge knots
  In this paper, we discuss the region unknotting number of different classes of 2-bridge knots. In particular, we provide region unknotting number for the classes of $2$-bridge knots whose Conway notation is $C(m,\ n), C(m,\ 2,\ m),$ $ C(m,\ 2,\ m\pm1)$ and $C(2,\ m,\ 2,\ n)$. By generalizing, we also provide a sharp upper bound for all the remaining classes of $2$-bridge knots. 
Vikash Siwach and Prabhakar Madeti
math.GT