Ducket Wall Swallet
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References
(1811) , A general view of the Agriculture and Minerals of Derbyshire., p.295., B. McMillan
(1969) , The Speleologist Vol.3., p.17.,
(1976) , D.C.A. N/L No.27., p.5., Derbyshire Caving Association
(2010) , Caves of the Peak District, p. 149, DCA