@book { QualityEnhancementinVoluntaryCarbonMarket,
    title = "Quality Enhancement in Voluntary Carbon Market",
    author = "Kathleen {Leonard}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836625944",
    url = "https://m.diplom.de/document/226550"
}