“…Service levels . Inventory levels Aronis et al (2004), Ashayeri et al (1996), Caglar et al (2004), Chang et al (2005), Cohen et al (1989Cohen et al ( , 1990Cohen et al ( , 1999, Dekker et al (1998), Diaz (2003, Fortuin (1980Fortuin ( , 1981, Hollier (1980), Kalchschmidt et al (2003), Kennedy et al (2002), Liu and Lee (2007), Schultz (2004), Sleptchenko et al (2005), Suomala et al (2002Suomala et al ( , 2004, Thonemann et al (2002), Wong et al (2005) 398 S.M. Wagner and E. Lindemann In the past three decades, literature on the planning and operational level of spare parts in most cases has focused on the determination of the optimal inventory level for parts (Huiskonen 2001, Kennedy et al 2002.…”