Review of "Semigroups of linear operators and applications" by J.A. Goldstein. R. Nagel — 1986 Semigroup forum
On the stability of strongly continuous semigroups of positive operators on L 2 ( μ ) G. Greiner; R. Nagel — 1983 Annali della Scuola Normale Superiore di Pisa - Classe di Scienze