A class of $4$-manifolds which have $2$-spines
نویسندگان
چکیده
منابع مشابه
The class of groups which have a subgroup of index 2 is not elementary
F. Oger proved that if A is a nite group, then the class of groups which are abelian-by-A can be axiomatized by a single rst order sentence. It is established here that, in Oger's result, the word abelian cannot be replaced by group. In 2] it was proved that, if A is a nite group, then the class of groups G which have an abelian subgroup H such that G=H is isomorphic to A can be axiomatized by ...
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ژورنال
عنوان ژورنال: Proceedings of the American Mathematical Society
سال: 1980
ISSN: 0002-9939
DOI: 10.1090/s0002-9939-1980-0560603-8