tweaks to #4427

Applied tweaks suggested by @javiereguiluz.
minor #4447 [Book] tweaks to #4427 (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Book] tweaks to #4427

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

Applied tweaks suggested by @javiereguiluz.

Commits
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caf927f tweaks to #4427