“…In the B-spline literature [11,17,19], the knot sequence is usually written with knots' multiplicities. However, in the isogeometric analysis literature, see e.g., [9,33], the knot vector is usually split into a vector carrying the partition of the interval and a vector containing continuity information (knot multiplicity). As in this paper the multiplicity is always four at every knot, we follow the latter notation and, throughout the paper, write X n without multiplicity, i.e., x k < x k+1 , k = 0, .…”