Subtype-specific activation of estrogen receptors by a special extract of Rheum rhaponticum (ERr 731R), its aglycones and structurally related compounds in U2OS human osteosarcoma cells - Möller, F; Zierau, O; Jandausch, A; Rettenberger, R; Kaszkin-Bettag, M; Vollmer, G (Phytomedicine, 2007)