1. Biondi A, Dagilytė E, Küçük E (2018) Solidarity in EU law: Legal principle in the making. Edward Elgar Publishing, Cheltenham/Northampton
2. Blanquet M (2009) L’Unione Européenne en tant que système de solidarité: la notion de solidarité européenne [The European Union as a system of solidarity: the notion of European solidarity]. In: Hecquard-Théron M (ed) Solidarité(s). Perspectives juridiques. Université Toulouse 1 Capitole, Toulouse, pp 155–195
3. Boute A (2020) The principle of solidarity and the geopolitics of energy: Poland v. Commission (OPAL pipeline). CML Review 57(3):889–914
4. Boutayeb C (2011) La solidarité dans l’Union européenne - éléments constitutionnels et matériels [Solidarity in the European Union: constitutional and material elements]. Dalloz, Paris, pp 137–154
5. Casolari F (2015) The principle of loyal cooperation: a ‘master key’ for EU external representation? In: Besson S, Levrat N (eds) L’Union Européenne et le droit international – The European Union and international law. Issy-les-Moulineaux: LGDJ-Lextenso éditions, Paris/Geneva, pp 91–125