def create_article_author_matrix(alist):
    """Creates a matrix articles x authors, marking with 1 the articles
    where the authors participated in.
    Input:  alist - list of articles in a data structure.
    Output: result - articles x authors binary matrix."""
    authors = []
    for a in alist:
        authors += a.authors
    uniq_authors = list(set(authors))
    result = map(lambda a: map(lambda author: author in a.authors,
        uniq_authors), alist)
    return result, uniq_authors
