$Z^0$--${Z^0}^\prime$ and ordinary-exotic fermion mixings revisited   using some special observables
  We investigate the mixing of an extra ${Z^0}^\prime$ with the standard $Z^0$ and mixings of exotic fermions with their standard counterparts through some precisely measured electroweak observables. These observables are geared to search for physics beyond the Standard Model. We observe that although most of such mixings are severely constrained by the recent LEP data, some of the mixing angles could still be rather large, awaiting future tests. 
Gautam Bhattacharyya