  Context: Software Engineering research makes use of collections of software
artifacts (corpora) to derive empirical evidence from. Goal: To improve quality
and reproducibility of research, we need to understand the characteristics of
used corpora. Method: For that, we perform a literature survey using grounded
theory. We analyze the latest proceedings of seven relevant conferences.
Results: While almost all papers use corpora of some kind with the common case
of collections of source code of open-source Java projects, there are no
frequently used projects or corpora across all the papers. For some conferences
we can detect recurrences. We discover several forms of requirements and
applied tunings for corpora which indicate more specific needs of research
efforts. Conclusion: Our survey feeds into a quantitative basis for discussing
the current state of empirical research in software engineering, thereby
enabling ultimately improvement of research quality specifically in terms of
use (and reuse) of empirical evidence.
