Charles Francis Atkinson and John Horace Round, 1911 Encyclopædia Britannica (1911)
“ A description of this earlier castle is given in the life of John, bishop of Terouanne (Acta Sanctorum, quoted by G. T. Clark, Medieval Mil. Architecture) :—“The rich and the noble of that region being much given to feuds and bloodshed, fortify themselves . . . and by these strongholds subdue their equals and oppress their inferiors. They heap up a mound as high as they are able, and dig round it as broad a ditch as they can. ”
