@article{article22c587bb,
title   = {The coordinate ring of an n-dimensional sphere and some examples of differentially simple algebras},
author = {Zhelyabin, V. N and Popov, A. A and Shestakov, Ivan P},
year = {2013},
doi = {10.1007/s10469-013-9242-9},
journal   = {Algebra and Logic}
}