Investigations of interactions mediated by neutral currents

The report is devoted to four-fermion interactions mediated by the neutral currents. The results from the second phase of LEP are presented, when the production of two massive bosons was possible with the increased energy of the e+e- collisions. It enabled for a direct test of nonabelian structure of the electroweak theory. The results concern the four-fermion production of the pairs of the ZZ bosons, single Z and Zγ* production as well as search for anomalous gauge bosons couplings. The large part of the report is devoted to experimental techniques, physics analyses and discussion of results. (author)