@article{DAN_1980_250_3_a15,
     author = {V. V. Smelov},
     title = {Approximation of piecewise-smooth functions by the eigenelements of two {Sturm--Liouville} problems},
     journal = {Doklady Akademii Nauk},
     pages = {573--577},
     publisher = {mathdoc},
     volume = {250},
     number = {3},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_250_3_a15/}
}