@article{SJ_1957-1958__1__A5_0,
     author = {Quan, Pham Mau},
     title = {Le principe de fermat en relativit\'e g\'en\'erale},
     journal = {S\'eminaire Janet. M\'ecanique analytique et m\'ecanique c\'eleste},
     note = {talk:5},
     pages = {1--12},
     publisher = {Secr\'etariat math\'ematique},
     volume = {1},
     year = {1957-1958},
     language = {fr},
     url = {http://www.numdam.org/item/SJ_1957-1958__1__A5_0/}
}