Summability of power series in several variables, with applications to singular perturbation problems and partial differential equations

Balser, Werner

Annales de la Faculté des sciences de Toulouse : Mathématiques, Volume 14 (2005) p. 593-608

Necessary and sufficient conditions for matrix summability methods to be stronger than multisummability

Balser, Werner; Beck, Andreas

Annales de l'Institut Fourier, Volume 46 (1996) p. 1349-1357