Jérémie Bettinelli École polytechnique Laboratoire d'informatique (LIX) 91128 Palaiseau Cedex FRANCE E-mail: firstname « . » lastname « at » normalesup « . » org Office: 2023 Phone: (+33) (0)1 77 57 80 61

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Finally, we may also consider general orientable surfaces with a boundary, that is, connected sums of tori with disks removed. To give an image of such a thing, recall the gluing of bike tubes from last section and remove a certain number of nonintersecting disks from it.