When you cite several sources with same name authors and the year of publication is the same, add the author’s first name initial in the in-text citation also to distinguish them:
Johansson (2017) and A. Johansson (2019) reported that…
Two studies (Johansson, R. 20217; Johansson, A. 2019) show that…
Johansson, A. (2019). Title of the book. Place of publication: Publisher.
Johansson, R. (2017). Title of the book. Place of publication: Publisher.