Page 255: I messed up some minus signs in the derivation of the Howard Semi-Circle theorem. In (4.157), the (U_max - U_min) should be (U_max + U_min). The same is true in the un-numbered equation between (4.158) and (4.159). That means the final result, (4.159) should have (U_max + U_min) on the left-hand side and (U_max-U_min) on the right-hand side.
References
Page 404: Reference [22] and [23] Darrigola -> Darrigol. (Sorry to Oliver Darrigol! I spelt his name correctly in the Electromagnetism book.)
My thanks to Christopher Tong (no relation), Preetham, and Taoxiang Wang for catching these typos.