  Citation networks can reveal many important information regarding the
development of science and the relationship between different areas of
knowledge. Thus, many studies have analyzed the topological properties of such
networks. Frequently, citation networks are created using articles acquired
from a set of relevant keywords or queries. Here, we study the robustness of
citation networks with regards to the keywords that were used for collecting
the respective articles. A perturbation approach is proposed, in which the
influence of missing keywords on the topology and community structure of
citation networks is quantified. In addition, the relationship between keywords
and the community structure of citation networks is studied using networks
generated from a simple model. We find that, owing to its highly modular
structure, the community structure of citation networks tends to be preserved
even when many relevant keywords are left out. Furthermore, the proposed model
can reflect the impact of missing keywords on different situations.
