"The Greatest Generation" fought in WW2 and gave birth to the baby boomers, then the baby boomers, followed by Generation X, and "Millenials". I've also seen reference to the older half of the millenials as Generation Y or 'Why'. I've never seen a common reference to generations before the Greatest Generation but there are certainly trends and fads with names, such as "flappers". However, that's like saying "Valley Girl" is the name of a generation.

So: Greatest Generation, Baby Boomers, Generation X, Millenials (Y and Millenials) which are roughly in 20 year increments.

To cite a specific source would be disingenuous as these are marketing terms that eventually make such an impact on the lexicon, they become defined.