Holder Inequalities and Bounds on the Masses of Light Quarks
  QCD Laplace sum-rules must satisfy a fundamental (Holder) inequality if they are to consistently represent an integrated hadronic cross-section. After subtraction of the pion-pole, the Laplace sum-rule of pion currents is shown to violate this fundamental inequality unless the up and down quark masses are sufficiently large, placing a lower bound on the 1.0 GeV MS-bar running masses. 
T.G. Steele, K. Kostuik, J. Kwan