@article{10_4064_fm61_4_2016,
     author = {Janusz Pawlikowski},
     title = {A characterization of $\boldsymbol {\Sigma }_{2}^{1}$ sets},
     journal = {Fundamenta Mathematicae},
     pages = {45--49},
     publisher = {mathdoc},
     volume = {236},
     number = {1},
     year = {2017},
     doi = {10.4064/fm61-4-2016},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm61-4-2016/}
}