@book{ 0-1694679543, title = {Some observations on the beryllium minerals from Mt. Antero, Colorado}, journal = {American journal of science}, author = {Penfield, Samuel Louis}, address = {New Haven, Conn.}, year = {1890}, language = {English}, url = {https://katalog.ub.tu-freiberg.de/Record/0-1694679543} }