Example:
* "The study found that 75% of participants experienced a positive outcome. (Smith, 2023)"
Incorrect:
* "The study found that 75% of participants experienced a positive outcome. (Smith, 2023)."
* "The study found that 75% of participants experienced a positive outcome (Smith, 2023)."
This rule applies to other punctuation marks as well, such as question marks and exclamation points.