I was saddened to hear about the passing of E. Earle Ellis. Way before it was common to ask how Paul cited Scripture, it was Ellis who over 50 years ago first published Paul's Use of the Old Testament, a book still widely used and valued today.
Moreover, I knew he had been working on his magnum opus, a commentary on 1 Corinthians (ICC). I hope whatever has been written thus far will still be published.
For those of you interested, here is an article Ellis published in 1993, "Jesus' Use of the Old Testament and the Genesis of New Testament Theology," BBR 3; 59-75.