Robert Louis Stevenson (2015). “The Strange Case of Dr. Jekyll and Mr. Hyde (Classic Unabridged Edition): Psychological thriller by the prolific Scottish novelist, poet and travel writer, author of Treasure Island, Kidnapped, Catriona, The Black Arrow and A Child's Garden of Verses”, p.10, e-artnow
Robert Louis Stevenson (2010). “The Strange Case of Dr. Jekyll and Mr. Hyde, El Extraño Caso Del Dr. Jekyll Y Mr. Hyde: English-Spanish Parallel Text Edition”, p.112, Lulu.com