1. J. H. Ahlberg, E. N. Nilson, J. L. Walsh,The theory of splines and their applications (1967), Academic Press, New York.
2. P. Blaga,Some even-degree spline interpolation, Studia Univ. «Babeş-Bolyai», Mathematica37, 1 (1992), 65–72.
3. P. Blaga, G. Micula,Polynomial natural spline functions of even degree, Studia Univ. «Babeş-Bolyai», Mathematica38, 2 (1993), 31–40.
4. M. N. El Tarazi, A. A. Karaballi,On even-degree splines with applications to quadratures, J. Approx. Theory60 (1990), 157–167.
5. M. S. Henry, K. Wiggins,Approximation theory methods for linear and nonlinear differential equations with deviating arguments, SIAM J. Math. Anal.12 (1981), 342–354.