@article{JAC_2004__19_2_a2,
     author = {Green, R.M.},
     title = {Acyclic heaps of pieces. {I.}},
     journal = {Journal of Algebraic Combinatorics},
     pages = {173--196},
     publisher = {mathdoc},
     volume = {19},
     number = {2},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JAC_2004__19_2_a2/}
}