Approximation by invertible elements and the generalized E-stable rank for A(D)_R and C(D)_sym , volume=109, url=https://www.mscand.dk/article/view/15180, DOI=10.7146/math.scand.a-15180, abstractNote=We determine the generalized E-stable ranks for the real algebra, C(D)_sym , of all complex valued continuous functions on the closed unit disk, symmetric to the real axis, and its subalgebra A(D)_R of holomorphic functions. A characterization of those invertible functions in C(E) is given that can be uniformly approximated on E by invertibles in A(D)_R. Finally, we compute the Bass and topological stable rank of C(K)_sym for real symmetric compact planar sets K., number=1, journal=MATHEMATICA SCANDINAVICA, author=Mortini, Raymond and Rupp, Rudolf, year=2011, month=Sep., pages=114–132