Sovereign debt crisis

Critically discuss the following statement: “Eurozone countries are more prone to experience a sovereign debt crisis than countries that are not part of a monetary union.”
Suggested questions to help you structure your essay
1:What is an optimum currency area?
2:Is the Eurozone an optimum currency area?
3:How fragile is the Eurozone?
4: Are members of the Eurozone more prone to experience a sovereign debt crisis?
References that may help you start
Pilbeam, K., 2013. International Finance, Palgrave Macmillan, 3rd Ed., Ch 16.
Copeland, L., 2014. Exchange Rates and International Finance, Prentice Hall, 6th Ed.,  Ch. 16.