@book{HufnagelRueth2007,
  author    = {Hufnagel, W. and R{\"u}th, D.},
  title     = {Internes Rechnungswesen, LE 1-5},
  address   = {Hagen},
  year      = {2007},
  language  = {mul}
}
@book{HufnagelTeutemacher2007,
  author    = {Hufnagel, W. and Teutemacher, T.},
  title     = {Betriebliches Rechnungswesen, Externes Rechnungswesen, LE 1-4},
  address   = {Hagen},
  year      = {2007},
  language  = {mul}
}