“…Such techniques have been the subject of a great deal of recent attention (cf. Babuska et al [8,9) and Thompson [29]) and are generally capable of introducing finer-meshes in regions where greater resolution is needed [1,2,3,6,14,15,22,26], moving meshes in order to follow isolated dynamic phenomena [1,2,5,20,22,26,281, or changing the order of methods in specific regions of the problem domain [17,21]. The utility of such adaptive techniques is greatly enhanced when they are capable of providing an estimate of the accuracy of the computed solution.…”