https://www.sciencedirect.com/science/article/abs/pii/S01676...
Link to full paper via sci-hub:
https://sci-hub.st/10.1016/j.scico.2021.102609
This appears to be a web page where the authors have posted links to their research, data, updates, etc:
https://sites.google.com/view/energy-efficiency-languages/
For transparency, I've posted these here recently:
https://news.ycombinator.com/item?id=39286827