Artificial Intelligence: A Modern Approach, Second Edition -- Extra Errata

I have a first printing of the hardcover edition of this book. I have confirmed these errata with Stuart Russell, but they are not listed on the official errata page.

• Section 15.2: The equation in the middle of page 545 reads b_{k+1:t} = Backward(b_{k+2:t}, e_{k+1:t}) However, the equation above (15.7) shows that e_{k+2:t} is used only for recursing, and is thus covered by the b_{k+2:t} term. The equation above should read b_{k+1:t} = Backward(b_{k+2:t}, e_{k+1})
• Section 15.2: Equation 15.9 begins with an alpha, though it should not. The probabilities need not add up to 1, since they are probabilities of sequences like {(rain,rain,rain,rain),(rain,rain,rain,sun)}, and either is unlikely in Palo Alto.