@article{700616,
     title = {Descriptive complexity of functions},
     booktitle = {General topology and its relations to modern analysis and algebra IV},
     series = {GDML\_Books},
     publisher = {Society of Czechoslovak Mathematicians and Physicist},
     address = {Praha},
     year = {1977},
     pages = {[214]-219},
     mrnumber = {MR0458396},
     zbl = {0402.54009},
     url = {http://dml.mathdoc.fr/item/700616}
}

Katětov, M. Descriptive complexity of functions, dans General topology and its relations to modern analysis and algebra IV, GDML_Books,  (1977), pp. [214]-219. http://gdmltest.u-ga.fr/item/700616/