New viewpoints, results and problems in the theory of Phragmén-Lindelöf H. J. Rossberg — 1976 Annales Polonici Mathematici
On Kingman's integral inequalities for approximations of the waiting time distribution in the queuing model GI/G/1 with and without warming-up time H. J. Rossberg; G. Siegel — 1974 Applicationes Mathematicae