“…A reasonably rich literature exists on this subject; see [1], [2], [8], [19], [24], [26], [27], [32], [33], [35], [37], [38], [39], [40], [41], [42], [43], [50], [52], [53], [54], [60], [66], [67], [69], [70], [71], [72], [73], [74], [75], [76], [77], [78].…”