@article{10_21136_MB_1999_125996,
     author = {Cal\'abek, Pavel},
     title = {Higher-order differential systems and a regularization operator},
     journal = {Mathematica Bohemica},
     pages = {337--349},
     publisher = {mathdoc},
     volume = {124},
     number = {4},
     year = {1999},
     doi = {10.21136/MB.1999.125996},
     mrnumber = {1722872},
     zbl = {0937.34015},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/MB.1999.125996/}
}