Institute of Geological Sciences 1:250,000 series Bouguer Gravity Anomaly map.
[London] :  Institute of Geological Sciences, 
1975-
Based on J.O.G. maps.
Index in B.G.S. box.
National Grid (landward areas); U.T.M. grid (seaward areas).
Sheet lines are those at JOG (1501 AIR) but numbering is different Article in Cartographical Survey 1975.