@article{JGG_2016_20_2_JGG_2016_20_2_a1,
     author = {N. Anghel },
     title = {Concurrency and {Collinearity} in {Hexagons}},
     journal = {Journal for geometry and graphics},
     pages = {159--171},
     publisher = {mathdoc},
     volume = {20},
     number = {2},
     year = {2016},
     url = {http://geodesic.mathdoc.fr/item/JGG_2016_20_2_JGG_2016_20_2_a1/}
}