SIGMA JOURNAL OF ENGINEERING AND NATURAL SCIENCES-SIGMA MUHENDISLIK VE FEN BILIMLERI DERGISI, cilt.9, sa.1, ss.31-38, 2018 (ESCI)
We consider the papers related to the spectrum and the trace formula of a differential operator of second order with unbounded operator coefficient. Reviewing them, we examine what the spectrum is and how to find the trace formula of the operator.