@book { SocialApprovalasanIncentive,
    title = "Social Approval as an Incentive",
    subtitle = "The Voluntary Provision of Public Goods in Social Production Communities",
    author = "Matthias {Greiff}",
    year = "2011",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1108399"
}