The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black-hole accretion events - Keel, W; Chojnowski, S; Bennert, V; Schawinski, K; Lintott, C; Lynn, S; Pancoast, A; Harris, C; Nierenberg, A; Sonnenfeld, A; Proctor, R (Monthly Notices of the Royal Astronomical Society, 2011)