On the existence of a certain cubic spline

We propose a constructive proof of the existence and uniqueness of a defect-1 parabolic interpolation non-periodic spline that does not require additional boundary-value conditions. An estimate of the interpolation error is obtained. Bibliography: 3 titles. Translated fromObchyslyuval'na ta Prykladna Matematyka, No. 81, 1997, pp. 124–129.