O thou daughter of the Kingdom! Thy letter was received. Thou hast written concerning the union, agreement and affinity amongst the believers
DAS.Diary notebooks and letters of Mirza Ahmad Sohrab, Dec. 1912 – Jun. 1915. English and Persian diary notebooks and letters held in the U.S. National Bahá’í Archives. Often quoted in other sources such as SW. Catalog entries are indexed by date and include only the English notebooks and letters. Letters from 1 Jul 1913 through 19 Oct. 1914 found here: https://bahai-library.com/sohrab_diary_letters_1913-1914