Source: https://www.researchgate.net/profile/Frederic-Carluer-2/publication/272999933_Vers_une_Europe_de_l'Est_homogene_une_analyse_en_termes_de_clubs_de_convergence/links/54f482930cf2eed5d734bc3d/Vers-une-Europe-de-lEst-homogene-une-analyse-en-termes-de-clubs-de-convergence.pdf