@book{https://resolver.caltech.edu/CaltechAUTHORS:20190528-135836556,
    title = "Active Galactic Nuclei",
    year = "1990",
    url = "https://resolver.caltech.edu/CaltechAUTHORS:20190528-135836556",
    id = "record",
    isbn = "978-3-540-53285-9",
    doi = "10.1007/3-540-31625-6"
}