Helbling, C. (1957). General Ulrich Wille: Carl Helbling. Fretz & Wasmuth.
Lua i Stíl Chicago (17ú heag.)Helbling, Carl. General Ulrich Wille: Carl Helbling. Zürich: Fretz & Wasmuth, 1957.
Lua MLA (8ú heag.)Helbling, Carl. General Ulrich Wille: Carl Helbling. Fretz & Wasmuth, 1957.
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