Title: World Society for Stereotactic and Functional Neurosurgery / European Society for Stereotactic and Functional Neurosurgery : 8th Meeting of the World Society for Stereotactic and Functional Neurosurgery/ 5th Meeting of the European Society for Stereotactic and Functional Neurosurgery, Zürich, July 1981 : Part III : Technical AdvancesSpecial Topic Issue