@article{10_37236_2146,
     author = {Aimin Xu},
     title = {Extensions of {Spivey's} {Bell} number formula},
     journal = {The electronic journal of combinatorics},
     year = {2012},
     volume = {19},
     number = {2},
     doi = {10.37236/2146},
     zbl = {1288.11027},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/2146/}
}