The Recursive Stopping Time Structure of the 3x + 1 function (2017), latest update link

New results on the stopping time behaviour of the Collatz 3x + 1 function (2015)

On the structure and the behaviour of Collatz 3n + 1 sequences (2014)

The Role of the Fibonacci Sequence in the Collatz 3n + 1 Function (2014)

Über die Struktur und das Wachstumsverhalten von Collatz 3n + 1 Folgen (2014)