@article{EMJ_2021_12_3_a6,
     author = {A. Yu. Savin and K. N. Zhuikov},
     title = {$\eta${-Invariant} and index for operators on the real line periodic at infinity},
     journal = {Eurasian mathematical journal},
     pages = {57--77},
     publisher = {mathdoc},
     volume = {12},
     number = {3},
     year = {2021},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EMJ_2021_12_3_a6/}
}