On the graph of a function in two variables over a finite field

@inproceedings{Ball2004OnTG,
  title={On the graph of a function in two variables over a finite field},
  author={Simeon Ball and Michel Lavrauw},
  year={2004}
}
We show that if the number of directions not determined by a pointset W of AG(3, q), q = ph , of size q2 is at least peq then every plane intersects W in 0 modulo pe+1 points and apply the result to ovoids of the generalised quadrangles T2(O) and T ∗ 2 (H).