请问国外那些机构测量牛顿万有引力常数

请问国外那些机构测量“Newtonian constant of gravitation ”牛顿万有引力常数？怎么跟他们联系？我想跟他们请教：Newtonian constant of gravitation 的测量误差分析问题。

参考网站：
（1）http://www.codata.org/index.html
CODATA, the Committee on Data for Science and Technology, is an interdisciplinary Scientific Committee of the International Council for Science (ICSU), was established 40 years ago.
（2）http://physics.nist.gov/cuu/Constants/index.html
Fundamental Physical Constants from NIST