Quasar luminosity and twin effects induced by filamentary and planar   structures
  We consider filamentary and planar large scale structures as possible refraction channels for electromagnetic radiation coming from cosmological structures. By this hypothesis, it is possible to explain the quasar luminosity distribution and, in particular, the presence of "twin" and "brother" objects. Method and details of simulation are given. 
S.Capozziello and G.Iovane