On the Maximal Sectorial Operators
  In this work, firstly the maximal sectorial linear relations are described. Later on, the discreteness of the spectrum of the linear maximal sectorial operators and asymptotical behaviour of the eigenvalues of such operators in terms of the eigenvalues of its real part are investigated. Finally, it is obtained one result for the differential operators for first order in the Hilbert space of vector functions in finite interval. 
Z. I. Ismailov and R. Ozturk
math.FA