1. Abraham, R., Keith, A., Koebbe, M., Mayer-Kress, G.: Computational unfolding of double-cusp models of opinion formation. Int. J. Bifurcat. Chaos 1 (2): 417–430(1991). Internet: https://www.researchgate.net/publication/258992753_Computational_Unfolding_of_Double-Cusp_Models_of_Opinion_Formation
2. Callahan, J.: The double cusp has five minima. Math. Proc. Camb. Phil. Soc. 84, 537–538 (1978)
3. Carnap, R., Bar-Hillel, Y.: An outline of a theory of semantic information (1952). Reprinted in Bar-Hillel, Y.: Language and information. Selected Essays on their theory and Application. Jerusalem, 221–274 (1952/1964)
4. Cassirer, E.: Das Erkenntnisproblem in der Philosophie der Wissenschaft der neueren Zeit (vol. III). Wissenschaftliche Buchgesellschaft, Darmstadt [first print 1920] (1994)
5. Cassirer, E.: Philosophie der Symbolischen Formen, 3 vol. Wissenschaftliche Buchgesellschaft, Darmstadt (1995) [1923/1925/1929] [English new translation: The Philosophy of Symbolic Forms. Routledge, London (2020)]