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| | Letter to Nicolaas Kuiper |
 | | The easiest way to see this is to consider a (3,2) knot, and observe that it projects stereographically to a (3,2) torus knot from (0,0,0,1) and to a (2,3) torus knot from (0,1,0,0). |
 | | When we do so, we find that in general the strip is immersed except at a number of points where "twisting" occurs, as well as a finite number of places where the planar projection of the original curve has a double point. |
 | | In the case of the torus knots above, the planar projection of the original curve will be locally convex, so the self- linking number of the image of the curve in 3-space can be read off as the algebraic number of crossing points. |
| www.geom.uiuc.edu /~banchoff/self-linking/NK.html (983 words) |
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