14  The “Five Presidents’ Report” (“Completing Europe’s Economic and Monetary Union”, a report prepared by J.-C. Juncker, in close cooperation with D. Tusk, J. Dijsselbloem, M. Draghi and M. Schulz, 22 June 2015) recommends integrating the intergovernmental solutions (the Treaty on Stability, Coordination and Governance in the Economic and Monetary Union, the Euro Plus Pact, the Intergovernmental Agreement on the Single Resolution Fund and the European Stability Mechanism) into the legal framework of the EU.
15  Cottarelli, C. and Guerguil, M. (eds. ), Designing a European Fiscal Union: Lessons from the Experience of Fiscal Federations, Routledge, 2014. 16  In particular, the economic literature uses as a criterion the comparison between, on the one hand, the heterogeneity of preferences and situations and, on the other, the externalities linked to different policies.