The convergence classes of Collatz function, Theoretical Computer Science, vol.412, issue.39, pp.5409-5419, 2011. ,
DOI : 10.1016/j.tcs.2011.05.056
The 3x+1 Problem and Integer Representations, p.2015 ,
On the combinatorial structure of 3N + 1 predecessor sets, Discrete Mathematics, vol.148, issue.1-3, pp.265-286, 1996. ,
DOI : 10.1016/0012-365X(94)00243-C