Add the letters a,b,c etc to distinguish between the different sources in both the citation and the corresponding reference in the reference list.
Petty (2021a) reports on the contributions from neonatal nurses of the impact of the COVID-19 pandemic. A mixed-methods approach was taken to explore the contribution of arts-based digital storytelling to understanding parental experiences of neonatal care (Petty, 2021b).
Compare the use of a,b,c in this citation example, with how the reference list would look.
This can be found in the “Journals … Multiple publications by the same authors in the same year” page.