@article{JRAM_1974__270_151493,
     author = {John Knopfmacher},
     title = {Arithmetical properties of finite rings and algebras, and analytic number theory. {IV.} {Relative} asymptotic enumeration and {L-series.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {97--114},
     publisher = {mathdoc},
     volume = {270},
     year = {1974},
     zbl = {0291.10036},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1974__270_151493/}
}