
|   X x W o------------------&gt;o Z x W
|         |                   |
|         |                   |
|         |                   |
|  proj_1 |                   | proj_2
|         |                   |
|         |                   |
|         v                   v
|       X o------------------&gt;o Z
|                   f
|
| Lang, DARM, pp. 30-31.
|
| Serge Lang,
|'Differential &amp; Riemannian Manifolds',
| Springer-Verlag, New York, NY, 1995.

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