deletions | additions       diff --git a/Introduction.tex b/Introduction.tex  index ff2bf3e..789d615 100644  --- a/Introduction.tex  +++ b/Introduction.tex 
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Consider the following system of signals:  $$  S = \{ (a_j, x_j) \}, \quad  j = 1, \ldots\, N $$  where a_j are signals amplitudes and x_j are signals positions. $\{a_j\}$ and $\{x_j\}$ may be represent by real or complex numbers. \par 
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