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*Proposition:*
If `S` is not empty and both `f`: **N**_{n} -> `S`
and `g`: **N**_{m} -> `S` are bijections, then
`n` = `m`:

( forallS!=0,ninN,minN,f:N_{n}->^{bijective}S,g:N_{m}->^{bijective}S:m=n).

*Proof:* see lecture notes.

*The size of a set is uniquely defined.*

Author: Wolfgang Schreiner

Last Modification: December 7, 1999