@article{10_4171_dm_448,
     author = {Mikhail Ershov and Wolfgang L\"uck},
     title = {The first $L^2${-Betti} number and approximation in arbitrary characteristic},
     journal = {Documenta mathematica},
     pages = {313--331},
     year = {2014},
     volume = {19},
     doi = {10.4171/dm/448},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/448/}
}