“…Now, there are three single-authored monographs in Gertler (1998), Chen and Patton (1999) and Mangoubi (1998). There are also several survey papers, of which we mention Isermann and Balle (1997), Isermann (1997) and Gertler (1997). The approaches to design suitable residuals are: parity space design (Chow and Willsky, 1984;Ding et al, 1999;Gertler, 1997), unknown input observer (Hong et al, 1997;Hou and Patton, 1998;Wang and Daley, 1996;Wunnenberg, 1990;Yang and Saif, 1998) and in the frequency domain (Frank and Ding, 199413;Sauter and Hamelin, 1999).…”