@incollection{JEDP_1989____A5_0,
     author = {Liess, Otto},
     title = {Global existence for the nonlinear equations of crystal optics},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {5},
     pages = {1--11},
     year = {1989},
     publisher = {Ecole polytechnique},
     doi = {10.5802/jedp.366},
     zbl = {0688.35091},
     mrnumber = {1030820},
     language = {en},
     url = {https://www.numdam.org/articles/10.5802/jedp.366/}
}