@Work{OL9068102W,
    title: {So lernt man lernen},
    author: {Sebastian Leitner},
    first_publish_year: {1987}
}

@Work{OL1303751W,
    title: {Représentation du monde chez l'enfant},
    author: {Jean Piaget},
    first_publish_year: {1929}
}

@Author{OL132393A,
    name: {Jean Piaget},
    birth_date: {1896}
    , death_date: {1980}
}