Hutchinson, Mary Anne, p. 1233. (EN) Hutchinson, Mary Anne, Gladys Mitchell, in Magill, Frank N. (a cura di), Critical Survey of Mystery and Detective Fiction, 3, Authors Ho-Pos, Pasadena, CA, Salem Press, 1988, OCLC471629189.
Hutchinson, Mary Anne, pp. 1233-1234. (EN) Hutchinson, Mary Anne, Gladys Mitchell, in Magill, Frank N. (a cura di), Critical Survey of Mystery and Detective Fiction, 3, Authors Ho-Pos, Pasadena, CA, Salem Press, 1988, OCLC471629189.