GAUSS an SCHUMACHER, 17. April 1849
Varia. Atlas des Erdmagnetismus Bd. 12, GDML_Books, (1929), p. 219 / Harvested from
Access to full text 
@article{PPN236060120+dmdlog127,
     title = {GAUSS an SCHUMACHER, 17. April 1849},
     booktitle = {Varia. Atlas des Erdmagnetismus Bd. 12},
     series = {GDML\_Books},
     year = {1929},
     pages = {219},
     url = {http://dml.mathdoc.fr/item/PPN236060120+dmdlog127}
}

 (éd.). GAUSS an SCHUMACHER, 17. April 1849, dans Varia. Atlas des Erdmagnetismus Bd. 12, GDML_Books,  (1929), p. 219. http://gdmltest.u-ga.fr/item/PPN236060120+dmdlog127/