@article{JIS_2007__10_2_a1,
     author = {Klazar,  Martin and Luca,  Florian},
     title = {Counting {Keith} numbers},
     journal = {Journal of integer sequences},
     year = {2007},
     volume = {10},
     number = {2},
     zbl = {1132.11006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2007__10_2_a1/}
}