1. Aarnio A (2011) The formal validity, efficacy, and acceptability of legal norms. In: Aarnio A (ed) Essays on the doctrinal study of law. Springer, Dordrecht, pp 125–130
2. Alexy R (2002) The argument from injustice. A reply to legal positivism. Oxford University Press, New York
3. Bobbio N (1993) Teoria generale del diritto. G. Giappichelli Editore, Torino
4. Bryde B-O (1993) Die Effektivität von Recht als Rechtsproblem. De Gruyter, Berlin/New York
5. Bulygin E (2007) Il positivismo giuridico. Giuffrè editore, Milano