@book{Alt1980,
  author    = {Alt, Helmut},
  title     = {Allgemeine Elektrotechnik, Nachrichtentechnik, Impulstechnik f{\"u}r UPN-Rechner. (Anwendung programmierbarer Taschenrechner ; 2)},
  publisher = {Vieweg},
  address   = {Braunschweig [u.a.]},
  isbn      = {3-528-04151-X},
  pages     = {VII, 109 S. : graph. Darst.},
  year      = {1980},
  language  = {de}
}
@book{Alt1980,
  author    = {Alt, Helmut},
  title     = {Elektrische Energietechnik, Steuerungstechnik, Elektrizit{\"a}tswirtschaft f{\"u}r UPN-Rechner. (Anwendung programmierbarer Taschenrechner ; 6)},
  publisher = {Vieweg},
  address   = {Braunschweig [u.a.]},
  isbn      = {3-528-04180-3},
  pages     = {VIII, 118 S. : graph. Darst.},
  year      = {1980},
  language  = {de}
}