Dictionary Used by the Guardian, by Universal House of Justice. (1997-12-08) Clarification/confirmation that the English dictionary used by Shoghi Effendi was Webster's (1934).
Life of Shoghi Effendi, The, by Helen Danesh, John Danesh, Amelia Danesh. (1991) Chapter length biography, and overview of the Guardian's life's work.
Shoghi Effendi: The Range and Power of His Pen, by `Alí Nakhjavání. (2006) The evolving style of the Guardian's writings; comparison of different periods of his writing; his translations; his writings in Persian and Arabic.