Classicly

Foundations of World Unity is a collection of talks and writings of `Abdu'l-Bahá, dated prior to his death in November 1921, and first published in 1945. The introduction to the 1945 edition is dated 1927.  It includes mainly selected talks from Promulgation of Universal Peace, and a few passages from Bahá'í Scriptures, Selections from the Writings of 'Abdu'l-Bahá and Some Answered Questions.