The last reference goes to Bradbury's dystopian novel Fahrenheit 451, which takes place in a post-atomic future. People spend most of their time in virtual 3D-TV-shows, whereas consuming and creating fantasies on their own by reading books is strictly forbidden. The hero of the story, Guy Montag, is working as a firman and as such he enters the homes of suspected individuals in order to burn their hidden libraries. Until at one point, he starts thinking - and reading - by himself. Bradbury was of course inspired by the German Nazi's infamous book burnings.
The title references the temperature at which Bradbury thought paper would start to ignite, which is why the number 451 is displayed on the firemen's uniforms and helmets.