Reuse published images I recently wrote an invited book chapter containing figures from different of my own papers that were previously published at ACM conferences. Can I reuse them (with citations to the original papers) without permission, or do I need some type of permission from ACM?
You almost certainly need permission. Check the publishing agreement you signed for each of the articles. They're probably all the same, but you might double check the copies you saved if they were in different years.