From Six Cities, Six Big Tech Ideas Coming to Boston on December 1: Stephen Wolfram to Keynote:

6x6: Six Cities, Six Big Tech Ideas (Dec. 1, 2011)
6×6: Six Cities, Six Big Tech Ideas (Dec. 1, 2011)

6×6: Six Cities, Six Big Tech Ideas. An Xconomy Forum in Boston on Dec. 1, 2011.