"Dirichlet was not satisfied to study Gauss' "Disquisitiones arithmeticae" once or several times, but continued throughout life to keep in close touch with the wealth of deep mathematical thoughts which it contains by perusing it again and again. For this reason the book was never placed on the shelf but had an abiding place on the table at which he worked....Dirichlet was the first one, who not only fully understood this work, but made it also accessible to others."