Retrieved 2 August 2013. (subscription required) Jackson and Murtomäki (eds), pp. 19 Stearns, David Patrick (3 January 2012).
Consultado o 2 de agosto de 2013. (require subscrición (?)).  Jackson and Murtomäki (eds), pp. 19 Stearns, David Patrick (3 de xaneiro de 2012).