1. On closed images of the space of irrationals;Engelking;Proc. Amer. Math. Soc.,1969
2. Ueber innere Abbildungen;Hausdorff;Fund. Math.,1934
3. Relativ perfekte Teile von Punktmengen und Mengen (A);Hurewicz;Fund. Math.,1928
4. Some theorems on selectors and their applications to semicontinuous decompositions;Kuratowski;Bull. Acad. Pol. Sci. Ser. Sci. Math. Astron. Phys.,1974
5. Topologie I;Kuratowski,1966