Complex sentence: Willi Schneider (1903--1971), brother of Rudi Schneider, was an Austrian spiritualist physical medium investigated by notable psychical researchers Harry Price, Albert von Schrenck-Notzing and Eric J. Dingwall, the Research Officer of the Society for Psychical Research.
Split into simpler sentences: Willi Schneider (1903--1971), brother of Rudi Schneider, was an Austrian medium. His physical medium was investigated by notable psychical researchers such as Harry Price, Albert von Schrenck-Notzing and Eric J. Dingwall, the Research Officer of the Society for Psychical Research.