http://op.gfz-potsdam.de/champ/

http://rsta.royalsocietypublishing.org/content/364/1841/1009.full

http://op.gfz-potsdam.de/grace/results/grav/g002_eigen-grace02s.html


http://pkukmweb.ukm.my/%7Erahim/gravity%20lecture(MSc).htm