Cita APA (7th ed.)

Sauerbrey, U. (2015). Friedrich Fröbel. Druckerei?.

Cita Chicago (17th ed.)

Sauerbrey, Ulf. Friedrich Fröbel. Erfurt?: Druckerei?, 2015.

Cita MLA (8th ed.)

Sauerbrey, Ulf. Friedrich Fröbel. Druckerei?, 2015.