Spohr, Louis: Duets for 2 violins. Duos Heft 1 / by L. Spohr. Provided with additional fingerings, bowings and sings of expression by C. Nowotny. Berlin [u.a.] : Schlesinger [u.a.], 18XX : 1(18XX). Berlin [u.a.] : Schlesinger [u.a.], [ca. 1890]. Badische Landesbibliothek Karlsruhe, DonMusDr 3028,2, https://nbn-resolving.org/urn:nbn:de:bsz:31-351098 / Public Domain Mark 1.0