  In the zero-dimensional systems, the Bratteli-Vershik models can be built
upon certain closed sets that are called `quasi-sections' in this article.
There exists a bijective correspondence between the topological conjugacy
classes of triples of zero-dimensional systems and quasi-sections and the
topological conjugacy classes of Bratteli-Vershik models. Therefore, we can get
refined Bratteli-Vershik models if we get certain refined quasi-sections. The
basic sets are such refined quasi-sections that bring `closing property' on the
corresponding Bratteli-Vershik models. We show a direct proof on the existence
of basic sets. Thorough investigations on quasi-sections and basic sets are
done. Furthermore, it would be convenient for the Bratteli-Vershik models to
concern minimal sets. To this point, we show the existence of the
Bratteli-Vershik models whose minimal sets are properly ordered. On the other
hand, we can get certain refinements with respect to the
Bratteli-Vershikizability condition or the decisiveness.
