@article{1365817,
      recid = {1365817},
      author = {Sommerhäuser, Yorck, and Zhu, Yongchang,},
      title = {Hopf algebras and congruence subgroups /},
      pages = {1 online resource (146 pages) :},
      note = {"September 2012 , Volume 219, Number 1028 (first of 5  numbers)."},
      url = {http://library.usi.edu/record/1365817},
}