Pavol Duris Juraj Hromkovic Stasys Jukna Martin Sauerhoff Georg Schnitger 49-75 2004 194 Inf. Comput. 1 http://dx.doi.org/10.1016/j.ic.2004.05.002 db/journals/iandc/iandc194.html#DurisHJSS04