Bartelt, M. W., et al. “A Generalized Interpolation Problem With Variable Nodes”.
Anal. Numér. Théor. Approx.
, vol. 6, no. 1, Feb. 1977, pp. 9-14,
https://ictp.acad.ro/jnaat/journal/article/view/1977-vol6-no1-art2
.