I currently use scholar.google.com to find papers in cases like Sophus Lie's original papers on "Transformation Groups". Does anyone know of other places that collect original works like this, i.e. works by those such as Weierstrass, Riemann or Lie describing the ideas that they originated. scholar.google.com isn't "bad" per se, I'd just like to look up just those papers and not every paper on the same topic.

I have access to many journals so that isn't so much the problem as knowing where to look.