Altman, E. (1968). Financial ratios, discriminant analysis, and the prediction of corporate
bankruptcy.The journal of Finance, 23 (4)
http://onlinelibrary.wiley.com/doi/10.1111/jofi.1968.23.issue-4/issuetoc,...
Altman,E. (1993). Corporate Financial Distress and Bankruptcy.John Wiley and Sons 2ª
Edition.New York.