I'm new to Evernote (used it years ago when it first came out and just didn't use it). And I'm also new to GTD- here is what I do. I just share the notebook, copy the notebook link (it'll be a public link) and add that to a project note. When I click the link it opens in a new tab and I have to answer the popup that asks how I'd like to view it every time- but at least I have a link to my reference material inside a project note. So for example- I have a project "Chicken Coop". I use my Project Info Sheet that I keep in my Template notebook (in reference) that has the project name, projected outcome, brainstorming (that I can review for next actions), and reference locations. In the reference locations I list links to any other places I have info on the chicken coop- like my pinterest board that has images for coop and run ideas, etc. (I already had this so no need to add each one to evernote), any google drive docs I may have already, and links to my chicken coop reference notebook- the shared notebook link. For now it will work- I'd love to be able to add a tag used for any notes I'd collected 'chickens' I guess creating the tag search and coping that link will have to do- great idea!