is mentioned by

Def Graph(x,y:T. R(x;y)) == < vertices = T, edges = {p:(TT)| R(1of(p);2of(p)) }, incidence = Id >	[rel-graph]
Def t.o == 2of(2of(2of(t)))	[gr_o]
Def Incidence(t) == 1of(2of(2of(t)))	[gr_f]
Def Edges(t) == 1of(2of(t))	[gr_e]
Def a[i] == 2of(a)(i)	[array-select]

In prior sections: core mb list 1 prog 1 graph 1 1

Try larger context: Graphs