@article{JIS_2008__11_4_a3,
     author = {Snapp,  Bart and Tracy,  Matt},
     title = {The {Collatz} problem and analogues},
     journal = {Journal of integer sequences},
     year = {2008},
     volume = {11},
     number = {4},
     zbl = {1196.11049},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2008__11_4_a3/}
}