“…These occur in many papers in Science and Engineering, e.g. [1,2,4,8,15,14,16,17,18,22,26,32,33,34,35,36,37,38,41,42], and several authors have analyzed the construction of nodal approximations mathematically, e.g. [9,10,11,19,20,24,40], but without considering optimal convergence rates.…”