@article{SLC_2001-2002_46_a1,
     author = {Elena Barcucci and Elisa Pergola and Renzo Pinzani and Simone Rinaldi},
     title = {ECO {Method} and {Hill-free} {Generalized} {Motzkin} {Paths}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {46},
     year = {2001-2002},
     url = {http://geodesic.mathdoc.fr/item/SLC_2001-2002_46_a1/}
}