20.24 chart:interpolation - definitions of b-spline and cubic-spine

I have written up a definition of a B-spline interpolation and attached
it as part of the description of 20.24 chart:interpolation.

Note that this is a real interpolation method, ie. the constructed
B-spline passes through all data points.

Andreas
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Andreas J. Guelzow
Concordia University College of Alberta