  Invited report at the 8th Meeting of the Working Group ``Base units and
fundamental constants'' of the French Academy of Sciences. June 14, 2004.
  The text consists of seven sections:
  1. Great importance of SI. 2. The necessity of updating SI. 3. Special
relativity: four-dimensional quantities. 4. Maxwell equations in vacuum in CGSG
units. 5. Maxwell equations in vacuum in SI. 6. $c \hbar$ units. 7. Systems
CGSG and $c \hbar$ should be legalized.
