In Zermelo-Fraenkel set theory $ZF$ consider the following statement defined for every field $K$: $B_K$ : Every vector space over $K$ has a basis. It is well-known that $AC \Rightarrow \forall K (B_K)$. A. Blass proved the converse. In his paper from 1984 he said that for a fixed field $K$, th...