CDF collaboration, Measurement of the tt-bar Production Cross Section in pp-bar Collisions at s**(1/2) = 1.96 TeV Using Dilepton Events,
Phys. Rev. Lett., vol. 93 no. 142001
(2004) [ps] .
Abstract:
http://www-cdf.fnal.gov/physics/preprints/cdf6882_top_dil_200pb_v7.html