Schwencke, Johann Friedrich : Adagio, Vl Orch, op. 36
| Johann Friedrich Schwencke an Louis Spohr in Kassel | Hamburg, Freitag 14. August 1840 | 1840081443 |
| Johann Friedrich Schwencke an Louis Spohr in Kassel | Hamburg, Sonnabend 6. Januar 1844 | 1844010643 |
| Louis Spohr an Johann Friedrich Schwencke in Hàmburg | Kassel, Montag 13. Mai 1844 | 1844051313 |
| Johann Friedrich Schwencke an Louis Spohr in Kassel | Hamburg, Sonnabend 3. August 1844 | 1844080343 |