Bujac, Mariana, and Petru Soltan. “The Abstract, Multidimensional Varieties and Their Classification”. Rev. Anal. Numér. Théor. Approx. 33, no. 2 (August 1, 2004): 163–165. Accessed May 5, 2024. https://ictp.acad.ro/jnaat/journal/article/view/2004-vol33-no2-art5.