I was reading the following paper: https://www.jstor.org/stable/2999442?seq=1#metadata_info_tab_contents
At one point there are a couple of simple passages that however I did not fully understand.
In particular, I can't figure out how a piece of the first term of (3) disappeared in the log linearization. And also how all three terms appear in the differentiation with respect to time (4).
Can anyone help me understand the steps? I offer a virtual beer, points, and much appreciation. Thank you!