<a href="https://en.wikipedia.org/wiki/Caerlaverock_Castle" class="extiw" title="en:Caerlaverock Castle">Caerlaverock Castle</a>, Scotland.
David MacGibbon and Thomas Ross
David MacGibbon, Thomas Ross, <i>The castellated and domestic architecture of Scotland</i>, vol. 1, Edinburgh : David Douglas, 1887, p. 134 (<a rel="nofollow" class="external text" href="https://archive.org/stream/castellateddomes01macg#page/134/mode/1up">online</a>).