Context : Margareta Gyllenstierna af Fogelvik (1689 - died 26 January 1740), was a politically active Swedish countess, married to Arvid Horn, the President of the Privy Council Chancellery (1710--1719 and 1720--1738) and one of the leading figures of the Swedish Age of Liberty. 
Question : What is Margareta Gyllenstierna's spouse's name?
Arvid Horn