Addendum/Erratum to the paper "Weyl groups and Birational transformations among minimal models"

We present an addendum/erratum to the paper "Weyl Groups and Birational Transformations among Minimal Models" written by the author and published in 1995, adding the analysis of the "88-th" deformation type of a smooth Fano 3-fold with $B_2 = 4$ denoted as $n^o\ 13$, which was missing from the original classification table by Mori-Mukai and added later to the list of smooth Fano 3-folds with $B_2 \geq 2$, while correcting the mistake pointed out by Eric Jovinelly (also noticed earlier by Kento Fujita). We also correct other typos and miscalculations, clarifying some points of ambiguity. The original paper is an attempt to generalize the result of Y. Manin associating some Weyl groups to Del Pezzo surfaces to the one associating certain Weyl groups to Fano 3-folds.