def first_word(title):
    """Find the first word in a title that isn't an article or preposition."""
    split_title = title.split()
    articles = ['a', 'an', 'the', 'some']
    prepositions = ['aboard','about','above','across','after','against','along','amid','among','anti','around','as','at','before','behind','below','beneath','beside','besides','between','beyond','but','by','concerning','considering','despite','down','during','except','excepting','excluding','following','for','from','in','inside','into','like','minus','near','of','off','on','onto','opposite','outside','over','past','per','plus','regarding','round','save','since','than','through','to','toward','towards','under','underneath','unlike','until','up','upon','versus','via','with','within','without']

    for word in split_title:
        if word.lower() not in articles and word.lower() not in prepositions:
            # '-' need to be removed for bibtex
            return word.lower().replace('-', '')