2Beckmann, Daniela, Lukas Menkhoff, Katja Sawischlewski. Robust Lessons about Practical Early Warning Systems [J]. Journal of Finance, 7(2006):56-60.
3Ciarlone, Alessio, and Giorgio Trebeschi. Designing an Early Warning System for Debt Crises [J]. Journal of Ac- counting Research, 9(2005) :109 - 114.
4Eckstein, Megan. Pension Shortfalls Put Pressure on Strained University Budgets [J]. Chronicle of Higher Educa- tion, 2(2009) :24-25.