Experimental Challenges for QCD - The past and the future
  The past leaves the surprising experimental successes of the simple constituent quark model to be expained by QCD. Surprising agreement with experiment from simple Sakharov-Zeldovich model (1966) having quarks with effective masses and hyperfine interaction. Nambu's (1966) Colored quarks with gauge gluons gave mass spectrum with only $qqq$ and $\bar q$ bound states. The future opens the way to new insight into QCD from heavy flavor experiments 
Harry J. Lipkin (Weizmann Institute, Tel Aviv University, Argonne)