@article{IM2_2002_66_5_a4,
     author = {D. D. Pervouchine},
     title = {On the closures of orbits of fourth order matrix pencils},
     journal = {Izvestiya. Mathematics },
     pages = {1047--1055},
     publisher = {mathdoc},
     volume = {66},
     number = {5},
     year = {2002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2002_66_5_a4/}
}