“…The problem has been known for years in the scheduling theory as a particularly hard combinatorial optimisation case. Although in the last three decades a lot of effort has been put into research in this area, good results have appeared quite recently, see state-of-the-art papers by Bl ażewicz, Domschke, and Pesch (1996), Vaessens, Aarts, and Lenstra (1996), and Jain and Meeran (1999), supplemented by a few recent studies (Jain, Rangaswamy, and Meeran, 2000;Pezella and Merelli, 2000;Nowicki and Smutnicki, 2001).…”