Complex sentence: In Great Britain, between 2 June and 13 July 1914, Tomczyk was tested in eleven sittings by the Society for Psychical Research, in informal experiments admittedly not subject to rigid control, with "inconclusive results".
Split into simpler sentences: In Great Britain, between 2 June and 13 July 1914, Tomczyk was tested in eleven sittings by the Society for Psychical Research. The informal experiments admittedly not subject to rigid control concluded "inconclusive results".