Per Sort

 @book{nmis09,
    address = {Bologna, Italy},
    apice = {NMis09},
    author = {Natali, Antonio and Molesini, Ambra},
    isbn = {9788874883349},
    month = {November},
    note = {second edition},
    publisher = {Esculapio},
    series = {Progetto Leonardo},
    title = {Costruire sistemi software: dai modelli al codice},
    year = 2009
} 

 @book{ing-soft08,
    address = {Bologna, Italy},
    apice = {IngSoft08},
    author = {Natali, Antonio and Molesini, Ambra},
    isbn = {9788874882007},
    month = {November},
    note = {Didactic publication},
    publisher = {Esculapio},
    series = {Progetto Leonardo},
    title = {La costruzione dei sistemi software: dai modelli al codice},
    year = 2008
}