A couple of years ago, I read his paper "Definitional Interpreters for Higher Order Languages" [1], because it was suggested to me by a friend. It was a joyful read, and to the best of my knowledge it is the first treatment of how to implement higher-order language constructs in a first-order language. Just recently, I thought of the paper, so it's sad news that the author has died...
[1] http://repository.readscheme.org/ftp/papers/plsemantics/reyn...