Here we have a resources page for links to relevant websites about double decker buses from their history.
For an incredibly detailed history of the Routemaster bus, from its design and conception, and uses, there is only one place to go: the Routemaster Association. It has all the facts and figures you will even need, and if they don’t, they know someone who does! to visit their site, follow this link: Routemaster Association
For some amazing pictures of early double decker buses, then look no further than the website of the London Transport Museum – follow this link: London Transport Museum.
For a great history of motorised buses in London, visit the website of the Museum of London here: Museum of London.
For everything Wikipedia has on the Routemaster bus, try here: Wikipedia.