Hájek, Petr,
Marek, Wictor W. and
Vopěnka, Petr. 2008.
“Mostowski and Czech-Polish Cooperation in Mathematical Logic.” in
Andrzej Mostowski and Foundational Studies, edited by Andrzej
Ehrenfeucht, Wictor W.
Marek, and Marian
Srebrny, pp. 403–405. Amsterdam: IOS Press.
Vopěnka, Petr and
Hájek, Petr. 1972.
The Theory of Semisets.
Studies in Logic and the Foundations of Mathematics n. 70. Amsterdam: North-Holland Publishing Co.