Peter Jansen
From Speedsolving.com Wiki

Peter Jansen is a Dutch speedcuber, and since 2003 a cohost of Speedcubing.com. He competed in 13 competitions between 2003 and 2010, including the revived World Rubik's Games Championship 2003.
Rotation notation
In 2001 he extended the standard cubing notation by adding x x' y y' z z'. He stated:
There are many websites that give the solutions for all the various cube positions you can run into when solving the cube using the 'Fridrich method', but most of them just give a set of moves. It takes a lot of time to adjust all the moves so that they can be executed at high speed. I adjusted many algorithms and added cube rotations to the standard notation to make it easy to see how the move can be performed.[1]
In 2002 Speedcubing.com changed its notation list to include x, y and z.(Before / After)
External links
 Peter Jansen's page on Speedcubing.com