An Improvement on Olson's Constant for Z_p+Z_p
  For a prime number p greater than 6000, the Olson's constant for the group Z_p+Z_p is given by Ol(Z_p+Z_p)=p-1+Ol(Z_p). 
Gautami Bhowmik (LPP), Jan-Christoph Schlage-Puchta