At fifteen Mary Sidney
became the third wife of Henry Herbert, Earl of Pembroke
; her dowry of £3,000 represented a heavy burden on her father
's finances.
Hannay, Margaret P. Philip’s Phoenix: Mary Sidney, Countess of Pembroke. Oxford University Press, 1990. http://U of A HSS, http://U of A HSS.
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Matthew, Henry Colin Gray, Brian Harrison, and Lawrence Goldman, editors. Oxford Dictionary of National Biography. http://www.oxforddnb.com/, http://www.oxforddnb.com/.