Geil, William Edgar.
The great wall of China. With one hundred full-page illustrations and maps. (London : John Murray, 1909). [Bericht der Reise entlang der Chinesischen Mauer].
https://archive.org/stream/greatwallofchina00geiluoft#page/n7/mode/2up.
(Geil3)
Travel and Legation Accounts