“…The solution gap of the combined objective values by the tabu search is within 6% even in tough cases with α = 0.9 and 0.8. ( 3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,8,8,8,8,8,8) 1.518 1.631 Tabu ( 3,3,3,3,3,3,3,4,4,4,4,5,5,5,5,5,6,6,6,6,6,7,7,7,8,8,8,12,12,16 ) 1.492 1.623…”