Lazarevic, Ilija. “On Best One-Sided Approximation With Interpolatory Families”.
Rev. Anal. Numér. Théorie Approximation
, vol. 3, no. 2, Aug. 1974, pp. 181-03,
https://ictp.acad.ro/jnaat/journal/article/view/1974-vol3-no2-art8
.