After I had sent offprints of m0y first paper on dimension theory to the Warsaw topologists in 1923, we regularly exchanged offprints of our publications. bout 1920, the Warsaw mathematicians had started a remarkable journal, the Fundamenta Mathematicae, unique in its devotion to abstract set theory, the theory of point sets, and the foundations of mathematics. Soon I was in correspondence with several contributors, especially Bronislaw Knaster and Kazimierz Kuratowski. In the autumn of 1929, the mathematicians of the University of Warsaw invited me there to deliver a lecture.