@article{CMUC_2007__48_2_a6,
     author = {M\'atrai, Tam\'as},
     title = {Covering $\Sigma^0_\xi$-generated ideals by $\Pi^0_\xi$ sets},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {245--268},
     publisher = {mathdoc},
     volume = {48},
     number = {2},
     year = {2007},
     mrnumber = {2338093},
     zbl = {1199.54189},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_2007__48_2_a6/}
}