@article{DAN_1957_115_5_a7,
     author = {L. D. Faddeev},
     title = {An expression for the trace of the difference between two singular differential operators of the {Sturm--Liouvilie} type},
     journal = {Doklady Akademii Nauk},
     pages = {878--881},
     publisher = {mathdoc},
     volume = {115},
     number = {5},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_115_5_a7/}
}