@article{TM2_2018_XXI_1_a0,
     author = {Jelena Kati\'c},
     title = {Substitutions in differential equations as a geometry of their symmetries},
     journal = {The Teaching of Mathematics},
     pages = {1 },
     publisher = {mathdoc},
     volume = {XXI},
     number = {1},
     year = {2018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TM2_2018_XXI_1_a0/}
}