APA (7th ed.) Citation

Walén, C. (1944). On the theory of sun-spots. Almquist & Wiksels.

Chicago Style (17th ed.) Citation

Walén, Claës. On the Theory of Sun-spots. Uppsala, Sweden: Almquist & Wiksels, 1944.

MLA (8th ed.) Citation

Walén, Claës. On the Theory of Sun-spots. Almquist & Wiksels, 1944.