@book{BachGisbert2008,
  author    = {Leonhard Emil Bach and Paul Gisbert},
  title     = {[Irmengarda <engl.> ] Irmengarda : grand' opera in due atti / di L. Emile Bach. [German text by P. Gisbert. Italian text by A. Zanardini. Engl. transl. by ...]},
  number    = {[Textbuch]},
  year      = {2008},
}