Oscar Wilde, Russell Jackson, Joseph Bristow, Ian Small (2000). “The Complete Works of Oscar Wilde: The picture of Dorian Gray : the 1890 and 1891 texts”, p.171, Oxford University Press on Demand
Horace Mann (1850). “A Few Thoughts for a Young Man: A Lecture, Delivered Before the Boston Mercantile Library Association, on Its 29th Anniversary”, p.38