@incollection{MSMF_1979__60__45_0,
     author = {Ekeland, Ivar},
     title = {Nonconvex duality},
     booktitle = {Analyse non convexe (Pau, 1977)},
     series = {M\'emoires de la Soci\'et\'e Math\'ematique de France},
     pages = {45--55},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {60},
     year = {1979},
     doi = {10.24033/msmf.260},
     mrnumber = {81c:49005},
     zbl = {0414.49014},
     url = {http://www.numdam.org/articles/10.24033/msmf.260/}
}