“…Subsequent researchers (see Mitra and Bhimasankaram, 1971;McGilchrist and Sandland, 1979;Haslett, 1985;Bhimasankaram et al, 1995;Bhimasankaram and Jammalamadaka, 1994a and Sengupta, 1999) sought to extend this work to data deletion, variable inclusion/exclusion, heteroscedastic and correlated model errors, rank-deficient V, rank-deficient X, inclusion/exclusion of multiple observations or variables, and so on. Another stream of research focussed on numerically stable methods of recursive estimation in the linear model (see, e.g., Chambers, 1975;Gragg et al, 1979;Kourouklis and Paige, 1981;Farebrother, 1988).…”