@article{10_21136_CMJ_1989_102323,
     author = {Neuman, Franti\v{s}ek},
     title = {Smoothness as an invariant property of coefficients of linear differential equations},
     journal = {Czechoslovak Mathematical Journal},
     pages = {513--521},
     publisher = {mathdoc},
     volume = {39},
     number = {3},
     year = {1989},
     doi = {10.21136/CMJ.1989.102323},
     mrnumber = {1006317},
     zbl = {0702.34034},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1989.102323/}
}