Hi Bernard,

I have been browsing a integrityware and npowersoftware websites for one hours. There is an astonishing gallery and video tutorial section about NURBS modeling. Considering that it might be a MoI's future, because the geometric kernel is the same.... whew...
The tutorial can be looked through this and this. One of them is about G1,G2,G3 continuity. Don't remember to switch on your speakers!

Petr