A letter report issued by the Government Accountability Office with an abstract that begins "Virtually all Department of Defense (DOD) weapon systems and equipment rely on power sources, such as batteries. In response to a mandate in the National Defense Authorization Act for Fiscal Year 2010, GAO determined (1) DOD's approximate investment in power sources, (2) the extent to which DOD coordinates its power source investments, and (3) the extent to which DOD's policies facilitate the use of standard power sources. To address these objectives, GAO obtained and analyzed DOD investment data, met with DOD officials and industry representatives, and attended DOD conferences aimed at facilitating power source coordination."