@article{ITA_1993__27_1_71_0,
     author = {Mitrana, Victor},
     title = {On languages satisfying {\textquotedblleft}interchange lemma{\textquotedblright}},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {71--79},
     publisher = {EDP-Sciences},
     volume = {27},
     number = {1},
     year = {1993},
     mrnumber = {1213422},
     zbl = {0770.68083},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1993__27_1_71_0/}
}