Soltan, P., and C. Prisăcaru. “On a Median for One Special Space”. Rev. Anal. Numér. Théor. Approx., vol. 26, no. 1, Aug. 1997, pp. 215-20, https://ictp.acad.ro/jnaat/journal/article/view/1997-vol26-nos1-2-art29.