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.
39
Matthew, Henry Colin Gray et al., editors. Oxford Dictionary of National Biography. http://www.oxforddnb.com/.