@article{AFST_1993_6_2_1_73_0,
     author = {Ovsienko, Valentin},
     title = {Lagrange schwarzian derivative and symplectic {Sturm} theory},
     journal = {Annales de la Facult\'e des sciences de Toulouse : Math\'ematiques},
     pages = {73--96},
     publisher = {Universit\'e Paul Sabatier},
     address = {Toulouse},
     volume = {Ser. 6, 2},
     number = {1},
     year = {1993},
     mrnumber = {1230706},
     zbl = {0780.34004},
     language = {en},
     url = {http://archive.numdam.org/item/AFST_1993_6_2_1_73_0/}
}