Aitken, W. H. M. H. (1894). The Difficulties of the Soul, or Hindrances to Believing. New York.
Lua i Stíl Chicago (17ú heag.)Aitken, W. Hay M. H. The Difficulties of the Soul, or Hindrances to Believing. New York, 1894.
Lua MLA (8ú heag.)Aitken, W. Hay M. H. The Difficulties of the Soul, or Hindrances to Believing. New York, 1894.
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