1. Alziary, B., Fleckinger, J., Lécureux, M.-H.: Principal eigenvalue and Maximum principle for some elliptic systems defined on general domains with refined Dirichlet boundary condition. Commun. Math. Anal. 7, 1–11 (2009)
2. Amann, H.: Fixed point equations and nonlinear eigenvalue problems in ordered Banach spaces. SIAM Rev. 18, 620–709 (1976)
3. Berestycki, H., Nirenberg, L., Varadhan, S.R.S.: The principal Eigenvalue and maximum principle for second order elliptic operators in general domains. Commun. Pure Appl. Math. 1, 47–92 (1994)
4. Birindelli, I., Mitidieri, E., Sweers, G.: Existence of the principal eigenvalue for cooperative elliptic systems in a general Domain, (Russian) Differ. Uravn 35, 325–333 (1999)
5. Brown, K.J., Lin, C.C.: On the existence of positive eigenfunctions for a eigenvalue problem with indefinite weight-function. J. Math. Anal. Appl. 75, 112–120 (1980)