@book { TarifbildungundIATAInterliningimLuftverkehr,
    title = "Tarifbildung und IATA-Interlining im Luftverkehr",
    author = "Ulrich {Steppler}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1103723"
}