62b.A21 [Canal du Nord to River Oise north of Bellicourt, March 24, 1917]
Tracing of defences from an aerial photograph (WWIAIR310, macrepo 4698, located in Box3, Envelope 63). It covers an area equivalent to squares A21, 27 and 28 on the corresponding WWI map sheet 62b. Annotations on recto: many tactical defences accompanied by a key to symbols and a north arrow. "PRINTED BY No. 3 ADVANCED SECTION. A.P.&S.S." printed in margin. WWI Aerial Photograph Collection: Box 3, Envelope 62.