[Fragment from an opera]

MLA

Guglielmi, Pietro, and Carlo Sernicola. [fragment From an Opera]. s.l, 17.

APA

Guglielmi, P., & Sernicola, C. (17). [Fragment from an opera]. s.l.

Chicago

Guglielmi, Pietro, and Carlo Sernicola. [fragment From an Opera]. s.l, 17.