The aim of the article is to indicate the biographical sources used by the author and to introduce some still unpublished biographical data of Josef Tvrdý. They are first of all materials deposited in the Archive of Masaryk University in Brno (Czech Republic) and of Comenius University in Bratislava (Slovak Republic). These approve the validity of biographical data published in this article. Among the new materials the most interesting are: the certificate affirming Tvrdý’s graduation from high school, the university record, administrative and personal letters, the report of the habilitation commission and various personal and autobiographical notes (mainly the reconstruction of his thesis defense and habilitation agenda) and the events related to his enforced leaving the Comenius University, his arresting and his death in the concentration camp Mauthausen.
*Príspevok je chránený zákonom o autorskom práve a právach súvisiacich s autorským právom (autorský zákon).