Retarded functional differential equations with nondense domain operators

In this work, we use integrated semigroups to state results on the existence and uniqueness of integral solutions and solutions for the abstract Cauchy problem x^′(t)=Bx(t)+Lx_t, t⩾0, where B is a nondensely defined linear operator on a Banach space X. This revised version was published online in June 2006 with corrections to the Cover Date.