pccm knot insertion question

I am stuck. I am attempting to implement "Patching Catmull Clark Meshes" from siggraph 2000 by Jorg Peters. I dont understand the knot insertion step, which I am told is really easy.

I need to insert three new knots at the endpoints to interpolate my nurbs patches. fine.

I need to insert three new control points to preserve the relationship beween degree,ctrl, and knots. fine.

what I dont understand are the rules for the new control points,

Q0 = (P-1 + 4P0 + P1)/6
Q1 = (P0 + 2P1)/3
Q2 = P1
Q3 = P2

how can I use these in a control array that already contains P1, P2 ??? Isnt that a problem?

I understand that when the spline function is evaluated, these guys will match up with P0, P0,P0, P0, but I feel like I am setting something up wrong, or miusunderstanding something.

-help!
Soren

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