1. Arnold BF, Stahlecker P (2002) Linear regression analysis using the relative squared error. Linear Algebra Appl 354: 3–20
2. Bandemer H, Gottwald S (1995) Fuzzy sets, fuzzy logic, fuzzy methods with applications. Wiley, New York
3. Gaffke N, Krafft O (1982) Matrix inequalities in the Löwner ordering. In: Korte B (eds) Modern applied mathematics, optimization and operations research. North-Holland Publishing Company, Amsterdam, pp 595–622
4. Kruse R, Gebhardt J, Klawonn F (1993) Fuzzy-Systeme (in German). Teubner, Stuttgart
5. Magnus JR, Neudecker H (1988) Matrix differential calculus with applications in statistics and econometrics. Wiley, New York