▎ 摘　　要

In this contribution we show that holonomy transformations are an efficient method to describe some geometrical characteristics. This approach is an alternative proceeding the Gauss-Bonnet theorem to get the deficit angle and it also permits to obtain the phase factor acquired by a vector which was parallel transported through a medium with topological defects. We have applied the holonomy transformation to the system described by Gonzalez and Herrero formed by two sheets of graphene connected by a carbon nanotube. The result confirms that the angle endowed is equivalent to 12 heptagonal carbon rings, which was shown by the authors.