Angular distribution of the secondary lepton in top-quark production followed
by subsequent semi-leptonic decay is studied assuming general top-quark
couplings. It is shown that the distribution does not depend on any possible
anomalous tbW couplings and is determined only by the standard V-A decay vertex
for any production mechanism if certain well-justified conditions are
satisfied.Comment: (1) PACS number changed (2) In Ref.[8], one typo corrected and one
paper (Erratum) added (3) To appear in Phys.Lett.