@article{CMUC_1980__21_1_a1,
     author = {\v{Z}\'ak, Stanislav},
     title = {A {Turing} machine oracle hierarchy. {I.}},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {11--26},
     publisher = {mathdoc},
     volume = {21},
     number = {1},
     year = {1980},
     mrnumber = {566238},
     zbl = {0429.68049},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1980__21_1_a1/}
}