indecomposable Λ-modules, the problem of determining the vector $ m (M)=(m_ {x}) _ {x∈
X}∈ ℕ^{X} $ such that $ M≅⨁ _ {x∈ X} X_ {x}^{m_ {x}} $ is studied. A precise formula for $
dim_ {k} Hom_ {Λ}(M, X) $, for any postprojective indecomposable module X, is computed in
Theorem 2.3, and interrelations between various structures on the set of all postprojective
roots are described in Theorem 2.4. It is proved in Theorem 2.2 that a general method of …