1. Appell, J., Zabrejko, P. P.: Nonlinear Superposition Operators. Cambridge University Press, Cambridge (1990)
2. Berestycki, B., Lions, P. L.: Existence of a Ground State in Nonlinear Equations of the Klein-Gordon Type. In: Variational Inequalities and Complementarity Problems (Proc. Internat. School, Erice, 1978), pp 35–51. Wiley, Chichester (1980)
3. Berninger, H.: Non-Overlapping Domain Decomposition for the Richards Equation via Superposition Operators. In: Domain Decomposition Methods in Science and Engineering XVIII, 169-176, Lect. Notes Comput. Sci. Eng, p 70. Springer, Berlin (2009)
4. Bourdaud, G.: Le calcul fonctionnel dans les espaces de Sobolev. Invent. Math. 104, 435–446 (1991)
5. Bourdaud, G.: Le calcul fonctionnel dans l’espace de Besov critique, (French) [Functional calculus in the critical Besov space]. Proc. Amer. Math. Soc. 116, 983–986 (1992)