Carl Du Prel

The philosophy of mysticism

George Redway, London 1889.

Joseph Jastrow

The psychology of spiritualism

The Popular Science Monthly, N. 46, Vol. XXXIV, London aprile 1889, pp. 721-732.

Proceedings of the Society for Psychical Research

Vol. 6, London 1889.

Journal of the Society for Psychical Research

Vol. 4, London 1889.