1. Ascensão, J. O. (2008). Direito Civil. Direito de Autor e Direitos Conexos, reprint. Coimbra: Coimbra Editora.
2. Beatson, J. (2002). Anson’s law of contract (28th ed.). Oxford: Oxford University Press.
3. Brehmer, N. (1992). Wille und Erklärung. Zu Geltungsgrund, Tatbestand und Zurechnung der Willenserklärung, Baden-Baden, Deutschland: Nomos Verlagsgesellschaft.
4. Carbonnier, J. (2000). Droit Civil. 4. Les obligations, Paris, France: Presses Universitaires de France.
5. Collins, A., Judge, G., & Rickman, N. (2007). On the economics of plagiarism. European Journal of Law and Economics, 24(2), 93–107.