@article{ITA_1999__33_3_259_0,
     author = {Borchert, Bernd and Kuske, Dietrich and Stephan, Frank},
     title = {On existentially first-order definable languages and their relation to {NP}},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {259--269},
     publisher = {EDP-Sciences},
     volume = {33},
     number = {3},
     year = {1999},
     mrnumber = {1728426},
     zbl = {0949.03035},
     language = {en},
     url = {http://archive.numdam.org/item/ITA_1999__33_3_259_0/}
}