變更

*[https://web.archive.org/web/20100118130724/http://home.uchicago.edu/~eoster/hbvnotecon.pdf "Hepatitis B Does Not Explain Male-Biased Sex Ratios in China"]

*[http://freakonomics.blogs.nytimes.com/2008/05/22/an-academic-does-the-right-thing/ "An Academic Does the Right Thing"] Freakonomics author Steven Levitt