1. See Piris supra note 4, at 143–48.
2. Tuytschaever Filip , EMU and the Catch-22 of EU Constitution-Making, in Constitutional Change in the EU: From Uniformity to Flexibility 173, 195 (Gráinne De Búrca & Joanne Scott eds., 2000).
3. See Haas Ernst B. , The Obsolescence of Regional Integration Theory (1975) (Univ. of California, Berkeley Inst. of Int'l Studies Ser. No. 25, 1975).
4. Sepos Angelos , Differentiated Integration in the EU: The Position of Small Member States 2 (Eur. Univ. Inst. Robert Schuman Ctr. for Advanced Stud., Working Paper No. 2005/17, 2005), available at http://www.eui.eu/RSCAS/WP-Texts/05_17.pdf.
5. See Paris, Berlin Hasten Plans for 'two-speed Europe', EurActiv.com (Nov. 28, 2011), http://www.euractiv.com/euro-finance/paris-berlin-hasten-plans-speed-europe-news-509243