1. E. Abakumov, Universal harmonic functions in the sense of Menchoff, private communication.
2. Universal properties of harmonic functions on trees;Abakumov;J. Math. Anal. Appl.,2017
3. E. Abakumov, V. Nestoridis, M. Picardello, Frequently dense harmonic functions and universal martingales on trees, in preparation.
4. Universal radial limits of holomorphic functions;Bayart;Glasg. Math. J.,2005
5. Frequently hypercyclic operators;Bayart;Trans. Am. Math. Soc.,2006