Vol. X: Restitution – Unjust Enrichment and Negotiorum Gestio. Chief Editor Peter Schlechtriem 3 Palmer, George E. History of Restitution in Anglo-American Law. 1989. 56 p. Vol. XVII: State and Economy. Chief Editors Richard Buxbaum and Ferenc Mádl 21 Hahn, Hugo J. / Gramlich, Ludwig Foreign Commerce and Investment – General Observations. 1989. 38 p. 22 Hahn, Hugo J. / Gramlich, Ludwig Foreign Commerce and Investment in Market Economy Countries. 1989. 96 p. 23 Mádl, Ferenc Foreign Commerce and Investment in Socialist Countries. 1989. 90 p.