On July 24, 1934, the Austrian mathematician Hans-Hahn died. Hans-Hahn (September 27, 1879 ¨C July 24, 1934) was an Austrian mathematician who made a significant contribution to philosophy and was a member of the Vienna Circle. Hans-Hahn's achievements in mathematics included the well-known Hahn-Bahnen theorem, and the equality of boundaries (independently derived by Panah and Stanhaus). Other theorems include the Hahn separation theorem, the Hahn-Hahn-Saxony theorem, the Hahn-Zuckiewicz theorem and the Hahn embedded theorem.