In this case, it's probably a response to the review paper that was recently published [1]. [1] Tao, Major challenges and opportunities in silicon solar module

In this case, it's probably a response to the review paper that was recently published [1]. [1] Tao, Major challenges and opportunities in silicon solar module recycling (July 2020) https://doi.org/10.1002/pip.3316 https://doi.org/10.1002/pip.3316