||I shall explain why the dates 1995 March 06, 2014 September 15, and 2016 January 14 are important for me.
For several centuries following its founding in 1477, all lectures and dissertations at Uppsala University were in Latin. Then, during one century, from 1852 to 1953, several languages came into use: there was a transition from Latin to Swedish, and then to French, German, and English. This transition is illustrated by language choice in doctoral theses in mathematics and in a Nordic journal.
Werner Fenchel was a pioneer in introducing duality in convexity theory. He got his PhD in Berlin, was forced to leave Germany, moved to Denmark, and lived during almost two years in Sweden. In a private letter he explained his views on the development of duality in convexity theory and the many terms that have been used to describe it. The background for his move from Germany is sketched.