TCG Letter #629 / Carpenter Letter #254

The Letters of J. R. R. Tolkien: Revised and Expanded ed. (HarperCollins, UK), pp. 480-81, p. 632 (Carpenter notes)

The Letters of J.R.R. Tolkien (1981), pp. 342-43, p. 451 (Carpenter notes)

Cartas de J.R.R. Tolkien, pp. 489-90, p. 643 (notas de Carpenter)

The J.R.R. Tolkien Companion and Guide - Chronology (2017), p. 648. (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.)

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

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