Sherlock holmes detected : the problems of the long stories - McQueen, Ian (Newton Abbot : David & Charles, 1974)
p. 218-219.
Keywords: Doyle, Arthur Conan, Sir, 1859 -- 1930 -- Characters; Doyle, Arthur Conan, Sir, 1859 -- 1930 -- Criticism and interpretation; Holmes, Sherlock (Fictitious character) -- Fiction; Detective and mystery stories, English -- History and criticism