@article{JIS_2015__18_2_a5,
     author = {Wang,  Yi and Zhang,  Zhi-Hai},
     title = {Combinatorics of generalized {Motzkin} numbers},
     journal = {Journal of integer sequences},
     year = {2015},
     volume = {18},
     number = {2},
     zbl = {1310.05015},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2015__18_2_a5/}
}