Petránek was a journalist for Czech Radio, the public radio broadcaster, at the time of the Prague Spring and the Warsaw Pact invasion of Czechoslovakia in 1968. He was fired by Czech Radio's management shortly after the invasion, but resumed underground, independent broadcasts during the country's Normalization period.
- Lazarová, Daniela (2018-11-11). "Czech Radio journalist Jan Petránek dies at 86". Radio Prague. Archived from the original on 2018-12-03. Retrieved 2018-12-03.
- "Journalist and commentator Jan Petránek dead at 86". Prague Daily Monitor. 2018-11-12. Archived from the original on 2018-11-16. Retrieved 2018-12-03.