Felsner, S., G. Joret, P. Micek, W. T. Trotter, and V. Wiechert. “Burling Graphs, Chromatic Number, and Orthogonal Tree-Decompositions”. The Electronic Journal of Combinatorics, Vol. 25, no. 1, Feb. 2018, p. P1.35, doi:10.37236/7052.