Cohomology in nonunitary representations of semisimple Lie groups (the   group $U(2,2)$)
  We suggest a method of constructing special nonunitary representations of semisimple Lie groups using representations of Iwasawa subgroups. As a typical example, we study the group   $U(2,2)$. 
A.M.Vershik, M.I.Graev
math.RT