Karpio, Andrzej, and Dorota Żebrowska-Suchodolska. 2016. “POLISH OPEN-END PENSION FUNDS PERFORMANCE AND ITS PERSISTANCE”.
Acta Scientiarum Polonorum. Oeconomia
15 (1), 15-25. https://js.wne.sggw.pl/index.php/aspe/article/view/4208.