@book{PPN51679308X, title = {Elemente der Quaternionen Bd. 2}, series = {GDML\_Books}, year = {1884}, zbl = {16.0616.02}, language = {ger}, url = {http://dml.mathdoc.fr/item/PPN51679308X} }
(éd.). Elemente der Quaternionen Bd. 2. GDML_Books (1884), http://gdmltest.u-ga.fr/item/PPN51679308X/