Customs - Correspondence with Nederlandsche Koloniale Petroleum Maatschappij, Sumatra
Customs questions - Correspondence with the Geneva Chamber of Commerce
Correspondence with the International Committee for European Economic and Customs Union.
Correspondence with La Revue petrolifère, Paris.
Customs - Correspondence with "Internationale Liga der Verbände von Geschäftsreisenden und Vertretern" (International League of Associations of Travelers and Trade and Industry Representatives)