George R. R. Martin (2012). “George R. R. Martin's A Game of Thrones 5-Book Boxed Set (Song of Ice and Fire Series): A Game of Thrones, A Clash of Kings, A Storm of Swords, A Feast for Crows, and and A Dance with Dragons”, p.402, Bantam
John Cotton Dana's remarks on a quotation suitable for inscription on a new building at Newark State College, Union, New Jersey (1912) as quoted in "The New York Times Book Review" (p. 55.), March 5, 1967.
Letter, 11 Nov. 1937, in Step by Step (1939) p. 186. Cf. the proverb "He who rides a tiger is afraid to dismount" (see Concise Oxford Dictionary of Proverbs under rides)