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来自维基词典,自由的词典
来自维基词典,自由的词典
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作為“空集”使用,最早出自布爾巴基小組在其論文《數學原本》(Éléments de mathématique)。安德烈·韋伊在其自傳中稱,他根據挪威語字母 Ø 造出該符號。[1]
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