片语
second countability第二可数公理
second countability axiom第二可数公理
countability languages可数语言
the second countability axiom第二可数公理
countability axioms可数性公理
denumerability可数性
enumerability[数] 可数性;[数] 可枚举性
first countability axiom第一可数公理
axiom of second countability第二可数公理
first axiom of countability第一可数公理
better fibrewise first countability强纤维第一可数
axiom of first countability第一可数公理