APA Style 6th Edition Blog: Abbreviations
https://blog.apastyle.org/apastyle/abbreviations/
Here’s the short version: Avoid contractions like "won't," "can't," "they're," and "it's." The first time you mention a phrase that can be abbreviated, spell it out in full and provide the abbreviation in parentheses. Use only the abbreviation thereafter. Only abbreviate phrases that occur three or more times in your paper. Avoid contractions like won’t, can’t, they’re, it’s.
Avoid contractions like "won't," "can't," "they're," and "it's."
The first time you mention a phrase that can be abbreviated, spell it out in full and provide the abbreviation in parentheses. Use only the abbreviation thereafter.
Only abbreviate phrases that occur three or more times in your paper.
Avoid contractions like won’t, can’t, they’re, it’s.
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