Kyselka, Daniel, and Marcela Efmertová. “Czechoslovak and Polish Intelligence (cryptologic) Services at the Time of the Institutionalisation of Both States and Their Armies After 1918”. Acta Polytechnica 64, no. 3 (July 9, 2024): 246–259. Accessed November 12, 2025. https://ojs.cvut.cz/ojs/index.php/ap/article/view/9670.