Bayerische Akademie der Wissenschaften <München>
| Franz Joseph Keppner an Louis Spohr in Kassel | München, Donnerstag 4. November 1852 | 1852110446 |
| Franz Joseph Keppner an Louis Spohr in Kassel | München, Donnerstag 4. November 1852 | 1852110446 |
| Franz Joseph Keppner an Louis Spohr in Kassel | München, Donnerstag 4. November 1852 | 1852110446 |
| Franz Joseph Keppner an Louis Spohr in Kassel | München, Donnerstag 4. November 1852 | 1852110446 |