def article_match_criterion(c1, c2):
    """
    check if two merge candidates(consisting of two nodes each) share an article
    :param c1: first merge candidate
    :param c2: second candidate
    :return: True iff the candidates share an article
    """
    if c1['art1'] == c2['art1'] or c1['art1'] == c2['art2']:
        return True
    if c1['art2'] == c2['art1'] or c1['art2'] == c2['art2']:
        return True
    return False