On pitfalls in computing the geodetic number of a graph. - Pierre Hansen; Nikolaj van Omme (Optim. Lett., 2007)

Packing 2×2 unit squares into grid polygons is NP-complete. - Dania El-Khechen; Muriel Dulieu; John Iacono; Nikolaj van Omme (CCCG, 2009)