def METHOD_NAME():
    """Get all paper references.
    Returns:
        Dict[str, List[str]]: keys are paper categories and values are lists
        of paper paths.
    """
    papers = glob('../src/papers/*/*.md')
    paper_refs = defaultdict(list)
    for fn in papers:
        category = fn.split(osp.sep)[3]
        paper_refs[category].append(fn)
    return paper_refs