Describe the mistake
Some equations contain text, such as (6.125). Note that "transformation of interest" and "inverse" are set in a different font from the main running text of the book, though it ought to be the same font. This could be a difference between the font used by \mathrm and the font used by \text: the former should be used for upright variables, the latter for actual text (English words). (And \operatorname for operators that aren't already pre-defined such as \exp.)
Location
Example (this occurs in other places, too, didn't note down all of them):
version (bottom of page)
Chapter 6.7
page 215 [pdf 221]
equation number (6.125)
Proposed solution
Assuming that's the cause, replace \mathrm with \text where applicable.
Describe the mistake Some equations contain text, such as (6.125). Note that "transformation of interest" and "inverse" are set in a different font from the main running text of the book, though it ought to be the same font. This could be a difference between the font used by
\mathrmand the font used by\text: the former should be used for upright variables, the latter for actual text (English words). (And\operatornamefor operators that aren't already pre-defined such as\exp.)Location Example (this occurs in other places, too, didn't note down all of them):
Proposed solution Assuming that's the cause, replace
\mathrmwith\textwhere applicable.