Orbiting valence quarks and their influence on the structure functions   of the nucleon
  It is shown that intrinsic orbital motion of the valence quarks has large influences on the spin-dependent as well as the spin-averaged nucleon structure functions. Its connection with the observed ``very small contribution of quark spin to nucleon spin'' and the observed violation of Gottfried sum rule is discussed. 
Liang Zuo-tang, R. Rittel