Experiment	Measurement	Reference
CDF	\([4.7 \pm 2.1\mbox{ (stat)} \pm 1.9\mbox{ (syst)}] \times 10^{-4}\)	PRD 55 1142 (1997)
Average	\(\mathbf{[4.7 \pm 2.8\mbox{ (combined)}] \times 10^{-4}}\)