[1] GRS80 - Wikipedia (2017-01-14 23:01:53 +09:00) <https://ja.wikipedia.org/wiki/GRS80>
[2] GEODETIC REFERENCE SYSTEM 1980 (2001-11-14 18:25:26 +09:00) <http://www.gfy.ku.dk/~iag/HB2000/part4/grs80_corr.htm>