Deze brief is afkomstig van iemand (naam ontbreekt) als antwoord op de brief die M. Jansen aan Tinbergen zond (bijlage) en Tinbergen vervolgens doorgestuurd heeft.
Letter is reply to a letter from mr. Ezekiel. With annexes: Previous letter from mr. Ezekiel and a first version of this article. The letter was answered by A.W.G. Koppejan since Tinbergen was on holiday. Tinbergen had already sent a reply earlier as well
