“…Researchers developed polynomially or pseudo-polynomially solvable algorithms for special cases where conditions for i α and i β are imposed (Cheng & Gupta, 1989;Hall et al, 1991;Hoogeveen & van de Velde, 1991;Kahlbacher, 1993). Studies employing meta-heuristics (Lee & Kim, 1995;James, 1997;Feldmann & Biskup, 2003;Hino et al, 2005) and dealing with this argument are even more recent. These recent published meta-heuristics do provide excellent results, but in some cases these meta-heuristics are so intricate that independent coding is unlikely to lead to the same effectiveness or efficiency.…”