Thank you, Gustavo! I am glad to find this forum.
The em dash explains the "publishing institutions," such as all levels of
government offices (local, state, national), research organizations, etc.
Before the sentence I submitted to the Grammar Exchange, I have: He would
identify various source materials. Then, he would send a letter....
I hope I made myself clear.
On Tue, Aug 4, 2020 at 5:59 PM The Grammar Exchange <firstname.lastname@example.org>