Let P be a set of n points in the plane in general position. A subset H of P consisting of k elements that are the vertices of a convex polygon is called a k-hole of P, if there is no element of P in the interior of its convex hull. A set B of points in the plane blocks the k-holes of P if any k-hole of P contains at least one element of B in the interior of its convex hull. In this paper we establish upper and lower bounds on the sizes of k-hole blocking sets, with emphasis in the case k=5
Cano, J., Garcia, A., Hurtado, F., Shakai, T., Tejel, F., URRUTIA, J. Blocking the k-holes of point sets in the plane. "Graphs and combinatorics", Setembre 2015, vol. 31, núm. 5, p. 1271-1287.