title: Response to letter by Spector and Lieblich.
authors.affiliation: a Department of Enterprise Engineering , University of Rome "Tor Vergata" , Rome , Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Patrizi
authors.affiliation: a Department of Enterprise Engineering , University of Rome "Tor Vergata" , Rome , Italy.
authors.forename: Ettore
authors.initials: E
authors.lastname: Pennestrì
authors.affiliation: a Department of Enterprise Engineering , University of Rome "Tor Vergata" , Rome , Italy.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Valentini