1. a Institut für Werkzeugmaschinen und Fabrikbetrieb, Technical University Berlin , Pascalstr. 8–9, 10587 Berlin, Germany
2. b Mechanical Engineering Department , University of Coimbra, Pỏlo II Pinhal de Marrocos , 3030 Coimbra, Portugal
3. c Department of Management Science , Lancaster University, Lancaster University Management School , Lancaster, LA1 4YX, UK