@book { TheEconomicsofVolunteerLaborSupply,
    title = "The Economics of Volunteer Labor Supply",
    subtitle = "An Application to Countries of a Different Development Level",
    author = "Susanne {Ziemek}",
    year = "2003",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1096140"
}