Multipoint Normal Differential Operators of Second Order
  In this work it is described all normal extensions of a multipoint minimal operator generated by linear multipoint differential-operator expression for second order in the Hilbert space of vector-functions in terms of boundary values at the endpoints of the infnitely many subintervals. Finally, a spectrum structure of such extensions has been investigated. 
E.Unluyol and E.Otkun Cevik and Z.I.Ismailov
math.FA