Uniformly ergodic theorem for commuting multioperators. Lahrech, Samir, Mbarki, Abderrahim, Ouahab, Abdelmalek, Rais, Said (2006) Electronic Journal of Differential Equations (EJDE) [electronic only]
Unitary equivalence and decompositions of finite systems of closed densely defined operators in Hilbert spaces [Book] Piotr Niemiec (2012)
Universal Spectra and Tijdeman's Conjecture on Factorization of Cyclic Groups. S. Szabó, J.C. Lagarias (2001) The journal of Fourier analysis and applications [[Elektronische Ressource]]