Property 8 for Regions of Convergence from Section 9.2 of the book:
"If the Laplace transform X(s) of x(t) is rational, then if x(t) is right-sided, the ROC is the region in the s-plane to the right of the rightmost pole. If x(t) is left-sided, the ROC is the region in the s-plane to the left of the leftmost pole."
