Ciesielski, Z., & Musielak, J. (1975). Approximation theory: Proceedings of the conference jointly organized by the Mathematical Institute of the Polish Academy of Sciences and the Institute of Mathematics of the Adam Mickiewicz University, held in Poznan, 22-26 August, 1972. Warszawa: PWN-Polish Scientific Publishers.

Ciesielski, Zbigniew, and Julian Musielak. Approximation Theory: Proceedings of the Conference Jointly Organized By the Mathematical Institute of the Polish Academy of Sciences and the Institute of Mathematics of the Adam Mickiewicz University, Held in Poznan, 22-26 August, 1972. Warszawa: PWN-Polish Scientific Publishers, 1975.

Ciesielski, Zbigniew, and Julian Musielak. Approximation Theory: Proceedings of the Conference Jointly Organized By the Mathematical Institute of the Polish Academy of Sciences and the Institute of Mathematics of the Adam Mickiewicz University, Held in Poznan, 22-26 August, 1972. Warszawa: PWN-Polish Scientific Publishers, 1975.