NP401(6) British Admiralty Sight Reduction Tables for Marine Navigation Vol 6 Lat 75° – 90°, 1971 Edition
The six volume series of Sight Reduction Tables for Marine Navigation is designed to facilitate the practice of celestial navigation at sea by the Marcq Saint Hilaire or intercept method. All the tables are equivalent with the US Pub. No. 229 and produced in cooperation with the Defense Mapping Agency in USA. The other volumes cover each 15 degrees of latitude.