@book { GermanCompaniesdoingBusinessinPostCommunistBulgariaLegalEconomicalAspects,
    title = "German Companies doing Business in Post Communist Bulgaria: Legal & Economical Aspects",
    author = "Kjell {Stein}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832478391",
    url = "https://m.diplom.de/document/223097"
}