[1] GRS80 - Wikipedia (1/14/2017, 2:01:53 PM) <https://ja.wikipedia.org/wiki/GRS80>

[2] GEODETIC REFERENCE SYSTEM 1980 (11/14/2001, 9:25:26 AM) <http://www.gfy.ku.dk/~iag/HB2000/part4/grs80_corr.htm>