@Work{OL880201W,
    title: {Essay concerning human understanding},
    author: {John Locke},
    first_publish_year: {1689}
}

@Work{OL815454W,
    title: {Doña Perfecta},
    author: {Benito Pérez Galdós},
    first_publish_year: {1886}
}

@Author{OL68704A,
    name: {Benito Pérez Galdós},
    birth_date: {1843}
    , death_date: {1920}
}