Margaret Buchanan (Douglas) - Looking for sources to validate the name of Thomas Buchanan's wife as Margaret Douglas

Looking for sources to validate the name of Thomas Buchanan's wife as Margaret Douglas.

So far, I can find only this - listing Thomas's sons without their mother's name:
"In the middle of the fifteenth century a Thomas Buchanan a brother of Patrick Buchanan of that Ilk, who was the grandson of Sir Walter bought a considerable number of estates in Stirlingshire and Perthshire. Guthrie Smith says, 1 ' a charter in his favour, granted by Patrick Buchanan of that ilk of the lands of Gartincaber .... is dated at Buchanan 1461.' He had also a charter dated at Torphichen, 3rd Feby., 1461-62, of the Temple Lands of Letter. On the 2nd October, 1472 . . . the bailie of Halden of Gleneagles gave sasine to ' Thomas Buchanan and Robert Makcalpyn of the lands of Ballvol and Camquhele.' In 1476 he purchased from Haldane of Gleneagles the lands of ' Kepdory, Carbeth, Ballawoul,' etc. In 1482 he conveyed Carbeth to his son Thomas, ' Ballyvow ' to his son Walter, and Kepdory to Robert his eldest son and heir apparent. In 1477 he acquired the Temple lands of Ballikinrain, in 1484 he had a charter from William, Lord Graham of Middle Ledlewan (the Moss). Besides these lands he bought Drumikil, half of which he gave to his son Robert in 1496. These charters and others prove that Thomas Buchanan was a successful money-making man."
GEORGE BUCHANAN: A MEMORIAL 1506-1906. Contributions by various writers, compiled and edited by D. A. MILLAR http://www.archive.org/stream/georgebuchananme00milliala/georgebuch...