Béla Bollobás, Imre Leader. Maximal sets of given diameter in the grid and the torus. Discrete Mathematics, 122(1-3):15-35, 1993. [doi]
@article{BollobasL93,
title = {Maximal sets of given diameter in the grid and the torus},
author = {Béla Bollobás and Imre Leader},
year = {1993},
doi = {10.1016/0012-365X(93)90284-Z},
url = {http://dx.doi.org/10.1016/0012-365X(93)90284-Z},
researchr = {https://researchr.org/publication/BollobasL93},
cites = {0},
citedby = {0},
journal = {Discrete Mathematics},
volume = {122},
number = {1-3},
pages = {15-35},
}