( 1) Ordnance Survey Map (Scale / Date)
OS 6" 1960
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( 2) Royal Commission on Historical Monuments (England) 1910 An inventory of the historical monuments in Hertfordshire
Page(s)74
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( 3) Aerial photograph
RAF CPE/UK/1917 3067-8 Jan 1947
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( 4) Field Investigators Comments
F1 NKB 08-FEB-73
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