maded more explicit that and where Dwyer-Kan gave the general definition:

- William Dwyer, Daniel Kan, Sec. 2.1 and Thm. 3.1 of:
*Singular functors and realization functors*, Indagationes Mathematicae (Proceedings) Volume 87, Issue 2, 1984, Pages 147-153 (doi:10.1016/1385-7258(84)90016-7)

added pointer to:

- Tammo tom Dieck, Section I.10 of:
*Transformation Groups*, de Gruyter 1987 (doi:10.1515/9783110858372)

added pointer to the original:

- Glen Bredon, Section I.3. of
*Equivariant cohomology theories*, Springer Lecture Notes in Mathematics Vol. 34. 1967 (doi:10.1007/BFb0082690)

added graphics showing the orbit categories of the first five cyclic groups (here)

]]>If you have time, please do!

]]>There is also another construction which goes by the name of “orbit category”: when $T : \mathcal{A} \to \mathcal{A}$ is an additive automorphism, the orbit category $\mathcal{A}/T$ is the one with the same objects as $\mathcal{A}$, and in which morphisms are given by $\mathcal{A}/T(X, Y) = \bigoplus_{i \in \mathbf{Z}} \mathcal{A}(X, T^i(Y))$. This has appeared under the name “orbit category” in papers of Keller, Tabuada, and others. Perhaps we should mention this somewhere on the page?

]]>The space induced by the backslash-comma combination looked too big to me. But never mind.

]]>The difference between the results of \mathrm{}\backslash, and \operatorname{} is invisible to my eyes.

]]>Some small changes at orbit category (including making $\mathrm{Or}\, G$ into $\operatorname{Or}G$ throughout).

]]>Since Mackey functor is only a stub, I added a ’Guide’ in the references

]]>added to *orbit category* a remark on what the name refers to (since I saw sonebody wondering about that)