The unitarity of permutations

Before we actually take up the subject of this section we must give a demonstration that permutations are unitary. This was deferred from above. 

The -particle spatial (or spin) functions we work with are elements of a Hilbert space in which the permutations are operators. If H(l, 2. )andT(I, 2. n) are two such functions we generally understand that 

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