  We examined software usage in a sample set of astrophysics research articles
published in 2015 and searched for source code for the software mentioned in
these research papers. We categorized the software to indicate whether source
code is available for download and whether there are restrictions to accessing
it, and if source code is not available, whether some other form of the
software, such as a binary, is. We also extracted hyperlinks from one journal's
2015 research articles, as links in articles can serve as an acknowledgment of
software use and lead to data used in the research, and tested them to
determine which of these URLs are still accessible. For our sample of 715
software instances in the 166 articles we examined, we were able to categorize
418 records as to availability of source code and found that 285 unique codes
were used, 58% of which offer source code available online for download. Of the
2,558 hyperlinks extracted from 1,669 research articles, at best, 90% of them
were available over our testing period.
