@book { Chineseurbanpoorolderpeopleslife,
    title = "Chinese urban poor older people’s life",
    author = "Jing {Xu}",
    year = "2012",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    doi = "10.3726/978-3-0351-0389-2",
    url = "https://www.peterlang.com/document/1052779"
}