@article{10_4153_CMB_1966_058_x,
     author = {Haruki, Hiroshi},
     title = {On the {Functional} {Equations} f(x+iy)| = |f(x)+f(iy)| and |f(x+iy)| = |f(x)-f(iy)| and on {Ivory's} {Theorem}},
     journal = {Canadian mathematical bulletin},
     pages = {473--480},
     year = {1966},
     volume = {9},
     number = {4},
     doi = {10.4153/CMB-1966-058-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1966-058-x/}
}