The two frenemies: China and Taiwan. Globe and Mail (Toronto), Dec. 29, 2009. http://www.theglobeandmail.com/report-on-business/rob-magazine/the-two-frenemies-china-and-taiwan/article1401058/
Note: millstone (n): "either of two circular stones used for grinding (as
grain) 2 a : something that grinds or crushes b : a heavy burden"
www.m-w.com
In the last sense, millstone is usually used in the phrase "{like} a
millstone around one's neck." This article merely adds "economic" before "
millstone" a