def citation_count(papers, key='ayjid', verbose=False):
    """
    Generates citation counts for all of the papers cited by papers.

    Parameters
    ----------
    papers : list
        A list of :class:`.Paper` instances.
    key : str
        Property to use as node key. Default is 'ayjid' (recommended).
    verbose : bool
        If True, prints status messages.

    Returns
    -------
    counts : dict
        Citation counts for all papers cited by papers.
    """

    if verbose:
        print "Generating citation counts for "+unicode(len(papers))+" papers..."

    counts = Counter()
    for P in papers:
        if P['citations'] is not None:
            for p in P['citations']:
                counts[p[key]] += 1

    return counts
Generates citation counts for all of the papers cited by papers.

    Parameters
    ----------
    papers : list
        A list of :class:`.Paper` instances.
    key : str
        Property to use as node key. Default is 'ayjid' (recommended).
    verbose : bool
        If True, prints status messages.

    Returns
    -------
    counts : dict
        Citation counts for all papers cited by papers.