During your PhD you will need some letters or documents like letters of recommendation, statements of purpose, rebuttal letters for a journal, and many more. (nextscientist.com)
Finally, here's Gary W. Yohe of Wesleyan University (who is also a signatory of the Journal rebuttal letter): (dotearth.blogs.nytimes.com)
This story has been mis - characterized as an official Sweedish rebuttal letter but it came from a skeptical group called the «Stockholm Initiative». (climateaudit.org)