@article{MZM_2006_79_2_a9,
     author = {Yu. N. Sirota and A. O. Smirnov},
     title = {The {Heun} {Equation} and the {Darboux} {Transformation}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {267--277},
     publisher = {mathdoc},
     volume = {79},
     number = {2},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2006_79_2_a9/}
}