So about a month ago I conducted a short study with 3 peers and presented it in the form of a research poster (and was not peer reviewed). It was conducted at an astronomical observatory and the poster was "published" in their summer proceedings, but no paper was submitted to a journal or anything like that. I'm interested in turning this poster into a paper to be submitted. Not word for word, but still using much of the same data, methods, and math, just with a slightly different focus. Basically just refine it. Anyways, I contacted the three people who I worked with and asked whether or not they would be interested in helping me refine the original study and write the paper, and only one of the three expressed any interest whatsoever. I obviously want to avoid plagiarism, so that's why I came for help. Should I list the other two people as coauthors or just mention them in acknowledgments? Or not mention them at all? Forgive me if I am missing something as I have never attempted to publish before. And I hope this is in the right section in the forum. Feel free to move it or whatever complies with forum rules. Thanks for any help!