Ordnance Survey of Northern Ireland [cartographic material] /

Various GSGS editions. Topographic map series of Northern Ireland with relief shown by contours, spot heights and hypsometric tints.; Military edition of original civilian series (published from 1960), with grid values and additional marginalia overprinted in magenta or red. Edition 1-GSGS, all sheets, 1965; edition 2-GSGS, all sheets, 1967-1969 (issued 1967-1970); edition3-GSGS, sheets 1,3,6,8 & 9, 1971-1980; edition 4-GSGS, sheets 1,3 & 6, 1975-80.; Includes example of Irish grid reference.; Hellyer, 1989, "Ordnance survey small-scale map indexes: 1801-1998" : 32M