1. The parabolic differential equations and the associated semi-groups of transformations;Feller, William;Ann. of Math. (2),1952
2. Semi-groups of transformations in general weak topologies;Feller, William;Ann. of Math. (2),1953
3. On the generation of unbounded semi-groups of bounded linear operators;Feller, William;Ann. of Math. (2),1953
4. American Mathematical Society Colloquium Publications, Vol. 31;Hille, Einar,1948
5. On the generation of semi-groups and the theory of conjugate functions;Hille, Einar;Kungl. Fysiografiska S\"{a}llskapets i Lund F\"{o}rhandlingar [Proc. Roy. Physiog. Soc. Lund],1952