Added Whitney’s original paper.

]]>Ab is in fact a symmetric monoidal category.

]]>Removed reference to vanished online pdf (now without link, as removed by previous editor) and replaced it by something written by Tim Gowers.

]]>Removed the link as it returned 404 not found.

Anonymous

]]>made notationally more explicit the forgetful functor $U \colon Ab \to Set$ involved in declaring the universal bilinear map (here)

]]>In the Definition-section I have made the quotient map $A \times B \to A \otimes B$ more explicit.

]]>added to *tensor product of abelian groups* the examples $A \otimes \mathbb{Z} \simeq A$ and $\mathbb{Z}_a \otimes \mathbb{Z}_b \simeq \mathbb{Z}_{LCM(a,b)}$.

have split off *tensor product of abelian groups* from *tensor product* and expanded slightly