def extract_doi_links(urls):
    """
    Try to find a DOI from a given list of URLs.

    :param urls: A list of URLs.
    :returns: First matching DOI URL, or ``None``.
    """
    doi_urls = [url for url in urls if "/doi/" in url]
    if len(doi_urls) > 0:
        return ("http://dx.doi.org" +
                doi_urls[0][doi_urls[0].find("/doi/") + 4:])
    else:
        return None