الإنترنت (EBID): https://www.britannica.com/topic/Encyclopaedia-Britannica-English-language-reference-work/Eleventh-edition-and-its-supplements — تاريخ
from the original on 2006-02-11. Retrieved 2016-12-27., EncyclopædiaBritannicaEleventhEdition, موسوعة بريتانيكا ↑ Princeton University Office of Communications
الإنترنت (EBID): https://www.britannica.com/topic/Encyclopaedia-Britannica-English-language-reference-work/Eleventh-edition-and-its-supplements — تاريخ
الإنترنت (EBID): https://www.britannica.com/topic/Encyclopaedia-Britannica-English-language-reference-work/Eleventh-edition-and-its-supplements — تاريخ