Simultaneous ROSAT, GINGA, VLA, IUE and Optical Observations of the Bright Quasar H1821 + 643 Kolman, M. ; Halpern, J. P. ; Shrader, C. R. ; Filippenko, A. V. ; Fink, H. H. ; Schaeidt, S. G. Abstract Publication: Frontiers of Space and Ground-Based Astronomy Pub Date: 1994 DOI: 10.1007/978-94-011-0794-5_115 Bibcode: 1994ASSL..187..695K