Spectroscopic Variability of NGC5548 and IC4329A on Timescales of Days to Years Haba, Y. ; Furuzawa, A. ; Okajima, T. ; Akimoto, F. ; Yamashita, K. ; Misaki, K. ; Kunieda, H. Abstract Publication: New Century of X-ray Astronomy Pub Date: 2001 Bibcode: 2001ASPC..251..356H