Tham khảo Rad (đơn vị)

  1. ↑ International Bureau of Weights and Measures (2008). United States National Institute of Standards and Technology, biên tập. The International System of Units (SI) (PDF). NIST Special Publication 330. Dept. of Commerce, National Institute of Standards and Technology. Truy cập ngày 29 tháng 5 năm 2012. 
  2. ↑ “NIST Guide to SI Units – ch.5.2 Units temporarily accepted for use with the SI”. National Institute of Standards and Technology.