A class of optimal eighth-order Steffensen-type iterative methods for   solving nonlinear equations and their basins of attraction
  This article concerned with the issue of solving a nonlinear equation with the help of iterative method where no any derivative evaluation is required per iteration. Therefore, this work contributes to a new class of optimal eighth-order Steffensen-type methods. Theoretical proof has been given to reveal the eighth-order convergence. Numerical comparisons have been carried out to show the effectiveness of contributed scheme. 
Anuradha Singh and J. P. Jaiswal
math.NA