Immersions biharmoniques dans une variété de Cartan-Hadamard

If (Nm+p,h) is a Cartan-Hadamard manifold such that Ric(h)⩾−G(rN(x)) where G(0)⩾1, G′⩾0 and G−1/2∉L1(+∞), then every proper biharmonic isometric immersion ϕ:Mm→(Nm+p,h) is harmonic.