@book{MSM_1938__92__1_0,
     author = {Morse, Marston},
     title = {Functional topology and abstract variational theory},
     series = {M\'emorial des sciences math\'ematiques},
     year = {1938},
     publisher = {Gauthier-Villars},
     number = {92},
     zbl = {0022.40403},
     language = {en},
     url = {https://www.numdam.org/item/MSM_1938__92__1_0/}
}