1. Approximationssätze für Halbgruppenoperatoren in intermediären Räumen;Berens;Schriftenreihe d. Math. Inst. Univ. Münster, H.,1964
2. Equivalent representations for the infinitesimal generator of higher orders in semi-group theory;Berens;Indag. Math.,1965
3. On the best approximation for singular integrals by Laplace transform methods;Berens,1964
4. Necessary and sufficient conditions in the theory of Fourier transforms;Berry;Ann. of Math.,1931
5. Lectures on Fourier Integrals;Bochner,1959