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{\bf Le Anh Vinh}
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{\bf On the Number of Orthogonal Systems in Vector Spaces over Finite Fields}
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Iosevich and Senger (2008) showed that if a subset of the
$d$-dimen\-sional vector space over a finite field is large enough, then
it contains many $k$-tuples of mutually orthogonal vectors. In this
note, we provide a graph theoretic proof of this result.



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