@article{10_4153_CJM_1969_076_2,
     author = {Hahn, K. T. and Mitchell, Josephine},
     title = {Generalization of {Schwarz-Pick} {Lemma} to {Invariant} {Volume}},
     journal = {Canadian journal of mathematics},
     pages = {669--674},
     year = {1969},
     volume = {21},
     number = {1},
     doi = {10.4153/CJM-1969-076-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1969-076-2/}
}