Simeon Ball. The number of directions determined by a function over a finite field. Journal of Combinatorial Theory, Series A, 104(2):341-350, 2003. [doi]
@article{Ball03,
title = {The number of directions determined by a function over a finite field},
author = {Simeon Ball},
year = {2003},
doi = {10.1016/j.jcta.2003.09.006},
url = {http://dx.doi.org/10.1016/j.jcta.2003.09.006},
researchr = {https://researchr.org/publication/Ball03},
cites = {0},
citedby = {0},
journal = {Journal of Combinatorial Theory, Series A},
volume = {104},
number = {2},
pages = {341-350},
}