def is_preprint(r):
    """
    Return whether the link is an arXiv preprint
    """
    ans = False
    journal = r.get('journal', None)
    if journal is not None:
        if 'arxiv' in r['journal'].lower():
            ans = True
    else:
        return True
    adsurl = r.get('adsurl', None)
    if adsurl is not None:
        if 'arxiv' in adsurl.lower() or 'astro.ph' in adsurl:
            ans = True
    return ans
