def parse_authors(auth_str):
    """returns list of all author last names from a string with `last_name,
    first_initial and last_name, first_inital and etc`
    :param auth_str: string containing all author names as exported by
        EndNoteX9 default BibTex export
    :type auth_str: str
    :return: list of author last names
    :rtype: list of str
    """
    a_list = auth_str.split(' and ')
    out = []
    for x in a_list:
        out.append(x.split(',')[0])

    return out