@article{MS2_1989__64_2_186113,
     author = {Vagn Lundsgaard Hansen},
     title = {The characteristic algebra of a polynomial covering map.},
     journal = {Mathematica Scandinavica},
     pages = {219--225},
     publisher = {mathdoc},
     volume = {64},
     number = {2},
     year = {1989},
     zbl = {0699.46036},
     url = {http://geodesic.mathdoc.fr/item/MS2_1989__64_2_186113/}
}