On the representation of orthogonally additive polynomials in $\ell_p$
  We present a new proof of a Sundaresan's result which shows that the space of orthogonally additive polynomials $\mathcal{P}_o(^k\ell_p)$ is isometrically isomorphic to $\ell_{p/p-k}$ if $k<p<\infty$ and to $\ell_\infty$ if $1\leq p\leq k$. 
A. Ibort, P. Linares, J. G. Llavona
math.FA