Subdivisions of the Polish People's Republic
The subdivisions of the Polish People's Republic changed several times from the Republic's inception in 1946 to the latest revision in 1999. The first subdivisions of the Republic involved the territories that were acquired in the west after World War II. They were subsequently reformed in 1946, 1950, 1957 and 1975.
Source: Wikipedia — Subdivisions of the Polish People's Republic (CC BY-SA 4.0)