The Luenberger Indicator and Productivity Growth: A Note on the European Savings Banks Sector
Jonhathan Williams, Nicolas Peypoch, Carlos Pestana Barros,
Applied Economics, vol. 43, 2011, p. 747-755.

Analysing the Determinants of Performance of Best and Worst European Banks: A Mixed Logit Approach
Carlos Pestana Barros, Cândida Ferreira, Jonhathan Williams
Journal of Banking and Finance, vol. 31, 2007, p. 2189-2203.