s-Indacene-1,3,5,7(2H,6H)-tetraone (‘Janus dione’) and 1,3-Dioxo-5,6-indanedicarboxylic Acid: Old and New 1,3-Indandione Derivatives - Krief, Pnina; Becker, James Y; Ellern, Arkady; Khodorkovsky, Vladimir; Neilands (the late), Ojars; Shapiro, Lev (Synthesis, 2004)