Spectrophotometry of the Seyfert 1 galaxy Mrk 509 from 1972-1993 near H beta Chuvaev, K. L. ; Doroshenko, V. T. ; Sergeev, S. G. ; Pronik, V. I. ; Mal'Kov, Yu. F. Abstract Publication: Astronomy Letters Pub Date: May 1997 Bibcode: 1997AstL...23..355C