“…Here the control is either a displacement of one of the ends of the string, 1 or an elastic force acting on one of the ends, 2 or a combined control is considered, namely, an elastic force, applied to the left end of the string and a displacement of the right end. 3 The problem of the transfer of the string from a rest position to a specified fixed position in a specified time, when the displacement of one of the ends of the string serves as the control was considered in Ref.…”