Source: Veugelers, Aiginger, Breznitz, Edquist, Murray, Ottaviano, Hyytinen, Kangasharju, Ketokivi, Luukkonen, Maliranta, Maula, Okko, Rouvinen, Sotarauta,
National Advanced School of Applied Statistics and Economics E.N.S.E.A. of Abidjan .
