1. Ferguson, D. (1969). The Question of Uniqueness for G.D. Birkhoff Interpolation Problems, J. Approx.Theory
2, 1–28.
2. Lorentz, G.G. (1972). Birkhoff Interpolation and the Problem of Free
Matrices, J. Approx. Theory
6, 283–290.
3. Lorentz, G.G. (1974). The Birkhoff Interpolation Problem: New Methods and Results, pp.481–501, in: Proceedings Int. Conference Oberwolfach, Birkhauser Verlag, Basel (ISNM25)
4. Lorentz, G.G. (1977). Coalescence of Matrices, Regularity and Singularity of Birkhoff Interpolation Problems, J. Approx. Theory
20, 178–190.
5. Nemeth, A.B. (1966). Transformations of the Chebyshev Systems, Math. Clij
8.(31), 315–333.