Getaneh, Mi sganaw2018-06-292023-11-092018-06-292023-11-091986-06http://10.90.10.223:4000/handle/123456789/5095The vlork discusses the basic "techniques of gauge theories. The problem of neutrino masses is examined and the limitations it imposes on i"he allowed numbel's of lepton and quark families Is analyzed. Ii" Is argued thai" several existing models of unified theories may not be r'ealistlc at allenFamily Problems In Particle PhysicsThesis