1. Arndt, H., Interpolation mit regulären Spline-Funktionen, Dissertation, Münster, 1974.
2. Baumeister, J., Extremaleigenschaften nichtlinearer Splines, Dissertation, München, 1974.
3. Braess, D. and Werner, H., Tschebyscheff-Approximation miteiner Klasse rationaler Splinefunktionen II, J. Approx-imation Theory 10, 379–399, (1974).
4. by a class of formulae based on rational approximation, Math. Comp. 19, 456–462, (1965).
5. based on a self-adjusting non- polynomial interpolant, Math. Comp. 20 11–20, (1966).