Some equations in the book would be correct by adopting the units in which c=1. There is no mention to this in the text, and most of the other equations don’t assume it, so wherever a c factor is not explicit, it has been considered as errata:

Page 9, in the two equations above “Changing velocity to move from one inertial frame…” x^1 should appear divided by c (this is not incorrect when c=1 is assumed, but then c should not appear in other places)

Page 11, eq (1.20), the energy E should appear divided by c (this is not incorrect when c=1 is assumed, but then c should not appear in other places)

Page 16, at the end line, it should say “Charm quark c with charge +2/3”

Page 17, first line, it should say “Strange quark s with charge -1/3”

Page 34, again, unless it is explicitely stated, he has not used units in which c=1, and so the expression of the D’Alembert operator just after (and of the one just before too) “the field equations corresponding to the Lagrangian given in this problem can be written as” should have a factor 1/c^2 that multiplies the time derivative (this is not incorrect when c=1 is assumed, but then c should not appear in other places)

Page 35, the same for the D’Alembert operator that appears three times above “This equation is called the sine-Gordon”(…) (this is not incorrect when c=1 is assumed, but then c should not appear in other places)

Page 46, the charge e is missing in eq (2.40). Instead of -iA_\mu it should be -ieA_\mu (in fact, it appears as q a bit later, in example 2.6, so the author is not using units in which e=1 either)

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