Higher Kurtz randomness
(with André Nies, Frank Stephan, and Liang Yu). Annals of Pure and Applied Logic 161 (2010), no. 10, 1280—1290.
I visited Liang Yu at Nanjing University, China in 2008 and 2009. The collaboration for this paper however was later done by email plus a strategy meeting in Marseille in 2009.