O. Ortega Moreno:
"An optimal plank theorem";
Proceedings of the American Mathematical Society, 149 (2021), 3; 1225 - 1237.
http://dx.doi.org/10.1090/proc/15228Electronic version of the publication:
https://www.ams.org/journals/proc/2021-149-03/S0002-9939-2021-15228-3/