1. Hayford, John F., , Spec. publ. no. 99, United States Coast and Geodetic Society, 1912,
2. Tables isostatiques;Heiskanen;Bull. Geodeslque,1931
3. World maps of the effect of Hayford zones 10, 9, 8, and 7 to 1;Heiskanen,1938
4. World maps of the secondary effect of undulation of the Geold;Heiskanen,1941