Cita APA (7a ed.)

Heller, S., & Scholtz, H. Progresive studies for the pianoforte. [ s.n.].

Cita Chicago Style (17a ed.)

Heller, Stephen, y Herr Scholtz. Progresive Studies for the Pianoforte. [S.L.]: [ s.n.].

Cita MLA (9a ed.)

Heller, Stephen, y Herr Scholtz. Progresive Studies for the Pianoforte. [ s.n.].