Spin and Flavor Content of Constituent Quarks and One-Spin Asymmetries   in Inclusive Processes
  We discuss a nonperturbative mechanism for one-spin asymmetries in inclusive hadron production. The main role in generation of this asymmetry belongs to the orbital angular momentum of quark-antiquark cloud in internal structure of constituent quarks. 
S. M. Troshin and N. E. Tyurin