As a user of Maple 13, namely in computations on General Relativity & Tensor Calculus, I would like to let you know I just got, using Maple 13, the WRONG SIGN (positive Riemann scalar curvature in stead of correct NEGATIVE Riemann scalar curvature) in studying a threefold used as a 'Public Space' by Milne many years ago.

The square of the distance on the said threefold is dE^2=dR^2+(c*t0)^2*sinh(R/(c*t0))^2*(dtheta^2+sin(theta)^2*dphi^2) and you might be interested...