Librería Samer Atenea
Kálamo Books
Librería Elías (Asturias)
Librería Kolima (Madrid)
Librería Proteo (Málaga)
This book, first published in 1962, is based on a series of lectures first given at Cambridge University in 1959 and 1960, dealing with ’psychical research’ - i.e. the scientific investigation of ostensibly paranormal phenomena.