Pلl-type interpolation: interchanging value- and derivative-nodes

In (simple) Pál-type interpolation the problem consists of finding a polynomial of degree n + m - 1 that has prescribed values at, say, n pairwise distinct points and prescribed values for the rth derivative r ⩾ 1 at (another) set of m distinct points. oblem is named regular if it has a unique solution for any set of data; this is equivalent to the homogeneous problem (all prescribed values are 0) having the trivial solution only. s paper the effect of interchanging the value-nodes and the derivative-nodes on the regularity of the problem is studied for several sets of nodes.