"A historical site sponsored by Barometer Wold of Merton," Negretti & Zambra, http://www.negrettiandzambra.co.uk/index.htm (accessed 03/31/2015)
"Negretti and Zmbra," Union List of Artist Names, The J. Paul Getty Trust, http://www.getty.edu/vow/ULANFullDisplay?find=(%13%11negretti+%13%11and+%13%11zambra)|%13%11negretti%11and%11zambra&role=&nation=&prev_page=1&subjectid=500033353 (accessed 03/31/2015)