@article{MS2_1983__53_166869,
     author = {Shinji Yamashita},
     title = {Functions with {H...} hyperbolic derivative.},
     journal = {Mathematica Scandinavica},
     pages = {238--244},
     year = {1983},
     volume = {53},
     zbl = {0543.30025},
     url = {http://geodesic.mathdoc.fr/item/MS2_1983__53_166869/}
}