@article{PPN592283860+DMDLOG_0006, title = {Sph\"arische Trigonometrie.}, booktitle = {Stereometrie Bd. 2, Abth. 2}, series = {GDML\_Books}, publisher = {Hahn}, year = {1877}, pages = {138}, url = {http://dml.mathdoc.fr/item/PPN592283860+DMDLOG_0006} }
(éd.). Sphärische Trigonometrie., dans Stereometrie Bd. 2, Abth. 2, GDML_Books, (1877), p. 138. http://gdmltest.u-ga.fr/item/PPN592283860+DMDLOG_0006/