Azimuthal anisotropy in high-energy heavy-ion collisions at RHIC   energies
  Directed and elliptic event anisotropy parameters measured in the experiments at relativistic heavy-ion collider are presented. The possible origin of the measured elliptic anisotropy parameter $v_2$ and its sensitivity to the early phase of the high-energy heavy-ion collisions are discussed. 
ShinIchi Esumi