['It', 'is', 'worth', 'stressing', 'at', 'this', 'stage', 'that', 'the', 'above', 'equation', 'can', 'be', 'obtained', 'from', 'the', 'effective', 'Lagrangian', '(', '6)Leff=−14FμνaFaμν+M2−FμνaFaμν', '.']