Set of Pairs
Set of Pairs

Main set.mm:
* theorems moved from GS's mathbox
* ~cnfldfunALT and ~upgrpredgv  added
* comments of ~structtocusgr and ~cffldtocusgr adjusted

AV's mathbox:
* Section "Set of unordered pairs added, including the definition `Pairs ` of the set of all unordered pairs over a given set and related theorems
* Theorem ~sprbisymrel that shows that there is a bijection between the subsets of the set of pairs over a fixed set and the symmetric relations on this set (first step of the proof to show that there is a bijection between the simple pseudo graphs over a fixed set of vertices and the symmetric relations on this set of vertices, as suggested by Gérard Lang).

metamath/set.mm,metamath/set.mm,metamath/set.mm