1. E. Almansi, Sull’integrazione dell’equazione differenziale Δ 2n u=0, Ann. Mat. (3) 2 (1899), 1–59.
2. Ü. Aksoy and A.O. Çelebi, Neumann problem for generalized n-Poisson equation, J. Math. Anal. Appl. 357 (2009), 438–446.
3. H. Begehr and T. Vaitekhovich, Iterated Dirichlet problem for the higher order Poisson equation, Le Matematiche XIII (2008), 139–154.
4. H. Begehr and T. Vaitekhovich, Green functions in complex plane domains, Uzbek Math. J. 4 (2008), 29–34.
5. H. Begehr, J. Du and Y. Wang, A Dirichlet problem for polyharmonic functions, Ann. Mat. Pure Appl. 187 (2008), 435–457.