BibTeX:
@incollection{AdibTaherzadeh1974,
  author = {Adib Taherzadeh},
  title = {The Seven Valleys: A Letter That Maps the Journey of the Soul},
  booktitle = {The Revelation of Bahá'u'lláh (Vol. 1 — Baghdád 1853-63)},
  year = {1974},
  publisher = {George Ronald},
}

APA:
Adib Taherzadeh. (1974). The Seven Valleys: A Letter That Maps the Journey of the Soul. In *The Revelation of Bahá'u'lláh (Vol. 1 — Baghdád 1853-63)*. George Ronald.

MLA:
Adib Taherzadeh. "The Seven Valleys: A Letter That Maps the Journey of the Soul." *The Revelation of Bahá'u'lláh (Vol. 1 — Baghdád 1853-63)*, George Ronald, 1974.

Chicago:
Adib Taherzadeh. "The Seven Valleys: A Letter That Maps the Journey of the Soul." In *The Revelation of Bahá'u'lláh (Vol. 1 — Baghdád 1853-63)*, George Ronald, 1974.