Measurements of the differential cross sections for e+e-→μ+μ- and e+e-→τ+τ- at values of s from 52 to 57 GeV are reported. The forward-backward asymmetries and the total cross sections for these reactions are found to be in agreement with predictions of the standard model of the electro-weak interactions. These measurements are used to extract values of the weak coupling constant gv egv l and gA egA l, where l = μ or τ.
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We thank the TRISTAN staff for the excellent operation of the storage ring. In addition we acknowl-"edge the strong support and enthusiastic assistance provided by the staffs of our home institutions. This work has been supported by the Japan Ministry of Education, Science and Culture (Monbusho), The US Department of Energy and National Science Foundation, the Korean Science and Engineering Foundation and Ministry of Education, and the Academia Sinica of the People's Republic of China.