http://www.mth.uct.ac.za/omei/gr/chap7/node3.html [Broken] Shouldn't eq 45 have a minus sign, looking at eq 29. Although I'm confused because the positive sign makes sense when comparing with the Newton-Poisson equation. I can't see a sign error in eq 29. (I believe the metric signature here is (-,+,+,+)) Anyone? thanks..