TCG Letter #383 / Carpenter Letter #350

The Letters of J.R.R. Tolkien (1981), p. 429

The J.R.R. Tolkien Companion and Guide - Chronology (2017), p. 811. (The T.C.B.S. was began during the Summer term 1911 at King Edward School. See various entries re. T.C.B.S. and TCBS.)

Cartas de J.R.R. Tolkien, p. 611

The Letters of J. R. R. Tolkien: Revised and Expanded ed. (HarperCollins, UK), pp. 601-02

J.R.R. Tolkien A Descriptive Bibliography, Di1, p. 350

The J.R.R. Tolkien Companion and Guide - Reader's Guide Part 2 (2017), pp. 1281-88 (entry for T.C.B.S.)

Tolkien Studies: An Annual Scholarly Review - Volume VIII 2011, "Robert Quilter Gilson, T.C.B.S" by John Garth, p. 68