@book{demo-001,
    author = "Hans Hagen",
    title  = "\BIBTEX, the \CONTEXT\ way",
    year   = "2013",
}

@book{demo-002,
    crossref = "demo-001"
    year     = "2014",
}

@book{demo-003,
    author  = "Hans Hagen and Ton Otten",
    title   = "Typesetting education documents",
    year    = "1996",
    comment = "a non-existing document",
}

@book{demo-004,
    author  = "Luigi Scarso",
    title   = "Designing high speed trains",
    year    = "2021",
    comment = "still to be published",
}

@book{demo-005,
    author = "author",
    title  = "title",
    year   = "year",
    serial = "serial",
    doi    = "doi",
    url    = "url",
    pages  = "pages"
}