Dryden, Henry. 1891. “Notes of the Brochs or Pictish Towers of Mousa, Clickemin, &C., in Shetland, Illustrative of Part of the Series of Plans and Sections Deposited in the Library of the Society”. Archaeologia Scotica 5 (November), 199-212. http://soas.is.ed.ac.uk/index.php/arch-scot/article/view/316.