Oberon plus classes and methods by H. Moessenboeck & J. Templ, 1989. See Oberon-2. ["object Oberon - An object-Oriented Extension of Oberon", H. Moessenboeck et al, ETH TR 109 (Apr 1990)]. ["object Oberon - A Modest object-Oriented Language", H. Moessenboeck & J. Templ, in Structured Programming 10(4), 1989].