Bühler, Ottmar Keywords: Double taxation | Treaties | Tax evasion | Mots clefs: Imposition (double) | Traités | Evasion fiscale | ABSTRACT Ottmar Buhler, in the introduction to this course, notes that the problems of tax law are due to a large number of states collecting taxes, multiplicity of the tax systems, and infinitely numerous and complicated economic relationships between countries. After a presentation of the different tax systems of the States of the world and economic relations between States giving rise t…