A method to find relations between the operators in the the mesonic Lagrangian of Chiral Perturbation Theory at order p6 is presented. The procedure can be used to establish if the basis of operators in the Lagrangian is minimal. As an example, we apply the method to the two-flavour case in the absence of scalar and pseudoscalar sources (s = p = 0), and conclude that the minimal Lagrangian contains 27 independent operators