Explicit evaluation of quadratic Euler sums
  In this paper, we work out some explicit formulae for double nonlinear Euler sums involving harmonic numbers and alternating harmonic numbers. As applications of these formulae, we give new closed form representations of several quadratic Euler sums through Riemann zeta function and linear sums. The given representations are new. 
Ce Xu, Yingyue Yang, Jianwen Zhang
math.NT