Observation of $\Upsilon(4S) decays to$\pi^+pi^-\Upsilon(1S)$ and $\pi^+pi^-\Upsilon(1S)$, report, April 19, 2006; (https://digital.library.unt.edu/ark:/67531/metadc874060/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .