@article{JDM_1912__21_145338,
     author = {Arthur Ranum},
     title = {Lobachefskian {Polygons} {Trignometrically} {Equivalent} to the {Triangle.}},
     journal = {Jahresbericht der Deutschen Mathematiker-Vereinigung},
     pages = {228--240},
     year = {1912},
     volume = {21},
     zbl = {43.0563.03},
     url = {http://geodesic.mathdoc.fr/item/JDM_1912__21_145338/}
}