1.1 Notation. As Bourbaki intended, we let N denote the set of finite cardinals, {0, 1, 2, . . .}. Throughout this section, let F be a field. We shall write dim(V ) to denote the F-dimension of an F-module V . Throughout this section, let (Z,VZ,EZ,EZ ι,τ −→ VZ) be a finite (oriented) graph; here, Z is a finite set, VZ ⊆ Z, EZ = Z −VZ, and ι and τ are functions. Each e ∈ EZ has an associated pic...