The distribution of seats was decided before the elections by the FJN, and electors had no possibility to change it. The results of the 1965 election would be duplicated, exactly, by the 1969 and 1972 elections.
Jerzy Drygalski, Jacek Kwasniewski, No-Choice Elections,Soviet Studies, Vol. 42, No. 2 (Apr., 1990), pp. 295–315, JSTOR
George Sakwa, Martin Crouch, Sejm Elections in Communist Poland: An Overview and a Reappraisal, British Journal of Political Science, Vol. 8, No. 4 (Oct., 1978), pp. 403–424, JSTOR
Informacja o dziatalnoici Sejmu PRL. (IV kadencja 1965-1969) (Warsaw: Sejm Chancellory Publications, 1969),