1. Alston P, Simma B (1992) The sources of human rights law: custom, jus cogens, and general principles. AYIL 12:82–108
2. Arnauld A (2014) Völkerrecht, 2nd edn. C.F. Müller, Heidelberg
3. Buzzini GP (2002) La théorie des sources face au droit international general. RGDIP 106:581–614
4. Cottier T, Muller JP (2012) Estoppel. In: Encyclopedia of public international law, Vol. III. Oxford University Press, Oxford, p 671 et seq
5. Crawford J (2012) Brownlie’s principles of public international law, 8th edn. Oxford University Press, Oxford