From Prof. Ley's list
Big 5 Book Publishing
https://indigoediting.com/new-york-publishing-big-5-basics/
https://www.thebalancecareers.com/the-big-five-trade-book-publishers-2800047
https://www.janefriedman.com/walk-away-good-big-5-publishers/
https://mspub.blogs.pace.edu/2017/10/09/internships-with-the-big-5/