Explanation to the map of Precambrian basement of the Gulf of Finland and surrounding area 1:1 mill. - Koistinen, Tapio J., 1939-; Laitakari, I.; Saltykova, T.; Amantov, A.; Pipping, F.; Vaasjoki, M.; Koistinen, T.; Virransalo, P.; Klein, V.; Koppelmaa, H.; Korsman, K.; Lahtinen, R.; et al. (Geological Survey of Finland, 1996)