@article{AM2_1984__27_137033,
     author = {Hiroshi Haruki},
     title = {On a functional equation for {Jacobi's} elliptic function cn(z; k).},
     journal = {Aequationes mathematicae},
     pages = {317--321},
     year = {1984},
     volume = {27},
     zbl = {0546.33001},
     url = {http://geodesic.mathdoc.fr/item/AM2_1984__27_137033/}
}