Bartelt, M. W., J. T. Lewis, and G. Meyers. “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.