Which text does the four sights story come from? One of the most famous stories of the Buddha is that of the four sights in which the Buddha sees old age, sickness death and a monk for the first time. However I read that this story doesn't actually occur in the Pali Canon. Can anyone give the reference for the text or texts that this story does occur in. 

Also since it doesn't appear in the Pali Canon is it reasonable to suppose that it might have less historical accuracy then other events in the Pali Canon. After all if it had of occurred wouldn't the Buddha have told Ananda at some point who would have then recounted when the storied were been collected after the Buddha's death. This is of a side point really - and probably unnecessarily contraversial.
Possibly a later development based on AN 3.39. In that sutta, the Buddha didn't explicitly mention He saw those signs but the ideas were there:


  ...Amid such splendor and a delicate life, it occurred to me: ‘An uninstructed worldling, though himself subject to old age, not exempt from old age, feels repelled, humiliated, and disgusted when he sees another who is old, overlooking his own situation. Now I too am subject to old age and am not exempt from old age. Such being the case, if I were to feel repelled, humiliated, and disgusted when seeing another who is old, that would not be proper for me.’ When I reflected thus, my intoxication with youth was completely abandoned...