@article{ITA_2008__42_2_253_0,
     author = {Hemmerling, Armin},
     title = {Hierarchies of function classes defined by the first-value operator},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {253--270},
     publisher = {EDP-Sciences},
     volume = {42},
     number = {2},
     year = {2008},
     doi = {10.1051/ita:2007031},
     mrnumber = {2401261},
     zbl = {1146.03032},
     language = {en},
     url = {http://www.numdam.org/articles/10.1051/ita:2007031/}
}