Abstract:
The estimate
$$
\Bigl|\sum_{x,1\dots,x_n\in F_q}\chi(f(x_1,\dots,x_n))\Bigr|\le(d-1)^nq^{n/2}.
$$
is derived for the quadratic character Lambda of a field $F_q$ of $q$ elements and a polynomial $f$ of odd degree $d$ over $F_q$ under certain natural conditions.