1. AAN, CZPK. (1957a). The letter of the undersecretary of state in the Heavy Industry Ministry to the general manager of Central Management of Cable Industry. June 26. AAN, CZPK, 633/120.
2. AAN, CZPK. (1957b). Inspection report prepared by State Ministry of Control. July 7. AAN, CZPK, 633/120.
3. AAN, CZZNTK. (1959). Inspection report of the Rolling Stock Repair Plant in Pruszków. AAN, CZZNTK, 1109/3/33.
4. AAN, Elkam. (1964a). The letters from Association of Cable Industry and Electrotechnology Equipment ‘Elkam’ to Cable Factory. April 20 and May 5. AAN, Elkam, 976/7/408.
5. AAN, Elkam. (1964b). The letters between Cable Factory and Association of Cable Industry and Electrotechnology Equipment ‘Elkam’ in the case of plan correction. January 1, February 14, October 17. AAN, Elkam, 976/5/444.