Mass of Pseudoscalar Gluonium: A Higher-Loop QCD Sum-Rule Estimate
  Higher-loop corrections to the pseudoscalar ($0^{-+}$) gluonium correlation function will be used to obtain the leading gluon condensate contributions to the subtraction-independent QCD sum-rules. The effect of these higher-loop corrections on the sum-rule estimates of the pseudoscalar gluonium mass will be investigated. The final results of this analysis compare favourably with $SU(3)$ lattice simulations. 
D. Asner, R.B. Mann, J.L. Murison and T.G. Steele