I give some links to the books and websites used for each chapter in the Resources section at the top of each chapter. Here are some more general suggestions:
Kennedys and Kings has some excellent research papers on a variety of topics. https://www.kennedysandking.com/
The most comprehensive online debate forum on the JFK Assassination is the Education Forum/JFK Assassination Debate: https://educationforum.ipbhost.com/forum/126-jfk-assassination-debate/
It's a good place to go to get some ideas on the pro's and con's over various evidentiary issues
Pat Speer is one of my favorite researchers. He's done great work on Dealey Plaza , the Medical Evidence, and he's the foremost researcher on the internal issues with the Warren Commission and HSCA: www.PatSpeer.com
Larry Hancock is another thoughtful person: https://larryhancock.wordpress.com/books-and-materials/ Larry has written a number of great books, including Someone Would Have Talked, Tipping Point, and The Oswald Puzzle
I use two sites for document searches. History-Matters.com has a good document search, but MaryFerrell.com has page level links. There are other document archives, like the City of Dallas, and Dallas Police which are often turned up with a simple Google search.
TangoDown63.com has a good collection of photographs, Dealey Plaza witnesses and essays