Stromberg, Karl (1972). “An Elementary Proof of Steinhaus's Theorem”. 《Proceedings of the American Mathematical Society》 36 (1): 308. doi:10.2307/2039082. JSTOR2039082.
jstor.org
Stromberg, Karl (1972). “An Elementary Proof of Steinhaus's Theorem”. 《Proceedings of the American Mathematical Society》 36 (1): 308. doi:10.2307/2039082. JSTOR2039082.