# PlanetPhysics/C 3CategoryCorollary

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\begin{corollary} (Corollary 1.3 in ref. [1].)


Any complete ${\displaystyle C_{3}}$-category ${\displaystyle {\mathcal {A}}}$ is a ${\displaystyle C_{2}}$-category.

\end{corollary}

[1]

## References

1. See p.83 in ref. ${\displaystyle [266]}$ , in the Bibliography for categories and algebraic topology