@article{UZKU_1969_129_3_a4,
     author = {A. Ya. Vol'pert},
     title = {Axiomatic definition of hyperbolic functions},
     journal = {U\v{c}\"enye zapiski Kazanskogo universiteta. Seri\^a Fiziko-matemati\v{c}eskie nauki},
     pages = {65--75},
     year = {1969},
     volume = {129},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/UZKU_1969_129_3_a4/}
}