Evidence for In-Medium Changes of Four-Quark Condensates
  Utilizing the QCD sum rule approach to the behavior of the omega meson in nuclear matter we derive evidence for in-medium changes of particular four-quark condensates from the recent CB-TAPS experiment for the reaction gamma + A -> A' + omega (-> pi0 gamma) with A = Nb and LH2. 
R. Thomas, S. Zschocke and B. Kampfer