“…Although these methods have been extensively studied theoretically since Babuska and Rheinboldt [5] and have also been successful in practice and become widely spread (see, e.g., [2,6,7,10,17,[31][32][33]40,41,43,45] and the references cited therein), their convergence for boundary value problems was not shown until the work by Dörfler [19]. The result in [19] was later extended by Dörfler and Wilderotter [20], Morin et al [30,31], Veeser [39], Binev et al [9], Mekchay and Nochetto [29], Stevenson [36] and Cascon et al [14] for the standard finite element method, Carstensen and Hoppe [12] and Chen et al [16] for the mixed finite element method, and Carstensen and Hoppe [13] for the nonconfroming finite element method.…”