Given a family $$\varphi = (\varphi_1, \ldots, \varphi_d)\in \mathbb{Z}[T]^d$$
of d distinct nonconstant polynomials, positive integer $$k\le d$$
and real parameter $$\rho$$
, we consider the mean value $$M_{k, \rho} (\varphi, N) \int_{{\rm x} \in [0,1]^k} \sup_{{\rm y} [0,1]^{d-k}}
| S_{\varphi}({\rm x}, {\rm y}; |^\rho \,d{\rm
$$
of exponential sums
$$S_{\varphi}({\rm \sum_{n=1}^{N} \...