@book { PublicSectorWagePremiuminPoland,
    title = "Public-Sector Wage Premium in Poland",
    author = "Gabriela {Grotkowska}",
    year = "2018",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b13439",
    url = "https://www.peterlang.com/document/1054904"
}