Geodesic
The Effect of Knot Modifications on the Shape of B-spline Curves
Journal for geometry and graphics, Tome 5 (2001) no. 2, pp. 111-12 
I. Juhasz; M. Hoffmann. The Effect of Knot Modifications on the Shape of B-spline Curves. Journal for geometry and graphics, Tome 5 (2001) no. 2, pp. 111-12. http://geodesic.mathdoc.fr/item/JGG_2001_5_2_a0/
@article{JGG_2001_5_2_a0,
     author = {I. Juhasz and M. Hoffmann},
     title = {The {Effect} of {Knot} {Modifications} on the {Shape} of {B-spline} {Curves}},
     journal = {Journal for geometry and graphics},
     pages = {111--12},
     year = {2001},
     volume = {5},
     number = {2},
     url = {http://geodesic.mathdoc.fr/item/JGG_2001_5_2_a0/}
}
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Voir la notice de l'article provenant de la source Heldermann Verlag

This paper is devoted to the shape control of B-spline curves achieved by the modification of one of its knot values. At first those curves are described along which the points of a B-spline curve move under the modification of a knot value. Then we show that the one-parameter family of k-th order B-spline curves obtained by modifying a knot value has an envelope which is also a B-spline curve of order k-1.