Sorry for the delayed response. You can get recent papers on PubMed. Searching the Digital Object Identifier (DIO) number can link you to a paper.
DOI: 10.1016/j.hrthm.2020.04.047
However, you can search for other articles precisely if you search the keywords separately regarding COVID-19 (e.g: ECG and COVID-19; PPG and COVID-19....).
If you need anymore assistance please feel free to contact me.