@article{ADM_2009_1_a5,
     author = {B. J. Gardner and M. M. Parmenter},
     title = {Some classes of directoid groups},
     journal = {Algebra and discrete mathematics},
     pages = {44--58},
     publisher = {mathdoc},
     number = {1},
     year = {2009},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2009_1_a5/}
}