If you cite several sources by the same author or group of authors, you’ll distinguish between them in your APA in-text citations using the year of publication.
If you cite multiple sources by the same author(s) at the same point, you can just write the author name(s) once and separate the different years with commas, e.g., (Smith, 2020, 2021).
To distinguish between sources with the same author(s) and the same publication year, add a different lowercase letter after the year for each source, e.g., (Smith, 2020, 2021a, 2021b). Add the same letters to the corresponding reference entries.