thallium
1981 / The Letters of William Crookes to Charles Hanson Greville Williams 1861–2: The Detection and Isolation of Thallium / Frank A. J. L James / Ambix 28 (1981) p. 131 [doi]
1984 / Of 'Medals and Muddles' the Context of the Discovery of Thallium: William Crookes's Early Spectro-Chemical Work / Frank A. J. L. James / Notes and Records 39 (1984) p. 65 [doi]