  Literature search is arguably one of the most important phases of the
academic and non-academic research. The increase in the number of published
papers each year makes manual search inefficient and furthermore insufficient.
Hence, automatized methods such as search engines have been of interest in the
last thirty years. Unfortunately, these traditional engines use keyword-based
approaches to solve the search problem, but these approaches are prone to
ambiguity and synonymy. On the other hand, bibliographic search techniques
based only on the citation information are not prone to these problems since
they do not consider textual similarity. For many particular research areas and
topics, the amount of knowledge to humankind is immense, and obtaining the
desired information is as hard as looking for a needle in a haystack.
Furthermore, sometimes, what we are looking for is a set of documents where
each one is different than the others, but at the same time, as a whole we want
them to cover all the important parts of the literature relevant to our search.
This paper targets the problem of result diversification in citation-based
bibliographic search. It surveys a set of techniques which aim to find a set of
papers with satisfactory quality and diversity. We enhance these algorithms
with a direction-awareness functionality to allow the users to reach either
old, well-cited, well-known research papers or recent, less-known ones. We also
propose a set of novel techniques for a better diversification of the results.
All the techniques considered are compared by performing a rigorous
experimentation. The results show that some of the proposed techniques are very
successful in practice while performing a search in a bibliographic database.
