 
  
  
   
Due to ergodicity of   , averaging over time and in
 , averaging over time and in   are
equivalent, and it is enough to proof the statements of the Theorem for
the
  are
equivalent, and it is enough to proof the statements of the Theorem for
the   -averaged squared distance:
 -averaged squared distance:
  
 
which equals I(t,u) for almost all u with respect to   .
 .
Straightforward calculations give:
  
 
(definition of q(t)),
  
 
(change of order of integration)
  
 
(definition of   ),
 ),
  
 
(change of independent variables,   ),
 ),
  
 
(definition of   )
 )
(convergence of   ).
 ).
  
 
(L'Hospital's rule). The last estimation is the statement (9) of the Theorem.
Analogously, using (10) in (32) in addition to (7) leads to a more accurate estimation (11).