His thesis was 1983, so it was well established by then. (It's not itself online, but in case anyone's curious, a description of a project using the work is at

His thesis was 1983, so it was well established by then. (It's not itself online, but in case anyone's curious, a description of a project using the work is at http://doi.org/10.1145/1096419.1096446 http://doi.org/10.1145/1096419.1096446 thanks to ACM now making all old papers free.)