부산대학교 도서관

The author considers the strong problem $u'(t)+A(t)u(t)=f(t)$ for $t\in[0,T]$ with $u(0)=u_0$ under conditions which do not require the closed unbounded operators $A(t)$ to be uniformly semi-bounded below. These seem to be the first general abstract results of this kind for the strong problem. The details can be found in the author's thesis [``Some aspects of abstract linear evolution equations in Hilbert space'', Ph.D. thesis, Univ. Illinois, Urbana, Ill., 1967] and will be published soon.