RT journal article T1 On vertices contained in all or in no metric basis A1 Hakanen, Anni A1 Junnila, Ville A1 Laihonen, Tero A1 González Yero, Ismael A2 Matemáticas K1 Cut-vertex K1 Forced vertex K1 Metric basis K1 Metric dimension K1 NP-hard K1 Pendant K1 Resolving set K1 Unicyclic graph AB A set R⊆V(G) is a resolving set of a graph G if for all distinct vertices v,u∈V(G) there exists an element r∈R such that d(r,v)≠d(r,u). The metric dimension dim(G) of the graph G is the cardinality of a smallest resolving set of G. A resolving set with cardinality dim(G) is called a metric basis of G. We consider vertices that are in all metric bases, and we call them basis forced vertices. We give several structural properties of sparse and dense graphs where basis forced vertices are present. In particular, we give bounds for the maximum number of edges in a graph containing basis forced vertices. Our bound is optimal whenever the number of basis forced vertices is even. Moreover, we provide a method of constructing fairly sparse graphs with basis forced vertices. We also study vertices which are in no metric basis in connection to cut-vertices and pendants. Furthermore, we show that deciding whether a vertex is in all metric bases is co-NP-hard, and deciding whether a vertex is in no metric basis is NP-hard. PB Elsevier SN 0166-218X YR 2021 FD 2021-12-21 LK http://hdl.handle.net/10498/29356 UL http://hdl.handle.net/10498/29356 LA eng DS Repositorio Institucional de la Universidad de Cádiz RD 12-nov-2026