1911 Encyclopædia Britannica (1911)
“ The family of the 4th marquess became extinct when George, the 5th marquess, died on the 4th of October 1770; and George, a son of the 3rd marquess, succeeded to the title. When he died unmarried on the 16th of November 1787 the marquessate passed to a kinsman, George (1733–1804) , a descendant of the 2nd marquess, who became 7th marquess. ”
