I have currently watched nine episodes of Durarara!! and I am surprised about how many references there are. Some are quite obvious (they even talk about Accel World or Spice and Wolf sometimes):
Some others not so obvious:
(It's the Baccano-screen.)
I can understand these, as all three are published by Dengeki Bunko, but why are there so many? Also, I don't understand why they included Yozakura Quartet, since it's a manga and no Light Novel?