an agreement between Iran and world powers over Iran's nuclear program. That letter outlined concerns about several provisions in the then-unfinished agreement and called for a number of improvements to strengthen the prospective agreement and win the letter-writers' support for it. The final agreement, concluded in July 2015, shows the influence of the letter. Post-Senate career A survey in October 2010 showed that Lieberman had an approval rating of 31% and that just 24% of Connecticut voters felt he deserved re-election. Lieberman announced on January 19, 2011 that he would retire from the Senate at the end of his fourth term. Lieberman gave his farewell address on December 12, 2012. He was succeeded by Democratic representative Chris Murphy. Following his retirement from the Senate, Lieberman became senior counsel of the white collar criminal defense and investigations practice at Kasowitz, Benson, Torres & Friedman, a law firm in New York City whose notable clients include Donald Trump. In March 2013, it was announced that Lieberman would be joining the conservative American Enterprise Institute think tank as co-chairman of their American Internationalism Project, alongside former Republican Senator Jon Kyl. In February 2014, Lieberman was named as Counselor at the National Bureau of Asian Research. Additionally, he serves as the Lieberman Chair of Public Policy and Public Service at Yeshiva University, where he teaches an undergraduate course in political science. In 2015, Lieberman served as co-chair of the Blue Ribbon Study Panel on Biodefense, a commission that recommended changes to U.S. policy regarding biodefense. In order to address biological threats facing the nation, the Blue Ribbon Study Panel on Biodefense created a 33 step initiative for the U.S. Government to implement. Joe Lieberman headed the organization with former Governor Tom Ridge, and the Study Panel assembled in Washington D.C. for four meetings concerning current biodefense programs. The Study Panel concluded that the federal government had little to no defense mechanisms in case of a biological event. The Study Panel's final report, The National Blueprint for Biodefense, proposes a string of solutions and recommendations for the U.S. Government to take, including items such as giving the vice president authority over biodefense responsibilities and merging the entire biodefense budget. These solutions represent the Panel's call to action in order to increase awareness and activity for pandemic related issues. In August 2015, Lieberman became chairman of the advocacy group United Against Nuclear Iran (UANI). In March