Many times while reading papers (especially engineering), many concepts, algorithms or results are taken for granted because they are already established in research. Sadly, at this point, many are not even referenced directly or some authors refer to other publications which use them. Is there a good and a fast method to find the original paper?
Here's the (horrible cheating) method that I use: if something is so well established that people don't bother referencing the original paper, then there's a good chance it's got an article on Wikipedia or Wolfram Mathworld or some other reference site. The references of such an article often include the original paper, but even if they don't they usually include something close enough in time that it does actually reference the original (or at least something closer to the point).
In many cases, however, you may not actually want the original: as the original becomes better understood, its presentation is often made much clearer and more succinct, and later textbooks or reviews may actually be the right source to point people at. For example, consider the difference between Newton's calculus, and calculus as it is now taught to undergraduates.