Covariant constraints of massive gravity in metric formulation

We propose a simple method to derive the constraints of the de Rham-Gabadadze-Tolley model in the Lagrangian formulation with the metric description, keeping the Lorentz covariance as far as possible. In our formulation, it is not necessary to use the Hamilton analysis, the vielbein formulation, nor the Stuckelberg trick in order to show the Boulwer-Deser ghostfreeness. It realizes the Lorentz covariant expressions of the constraints in a certain parameter region.