@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" }