“…In Dykstra's method, as in many other iterative projection schemes, it is assumed that the projections onto each of the individual sets i are relatively simple to compute, e. g., boxes, balls, half-spaces, and subspaces. The algorithm has been modified and used for many different applications; see, e. g., [1,11,18,19,27,29,30,35,36,38,39,[46][47][48][49]52]. For a review on Dykstra's method, and many other alternating projection schemes, see [4,5,10,13,20,31,32].…”